Dillon's torn car, with its engine already resting on another part of the racetrack, ended up on its roof and then was smashed into by Brad Keselowski's car.
"I'm shocked that Austin Dillon is even alive from what he went through," said Jimmie Johnson, who finished second toDale Earnhardt Jr."It was just a frightening moment. I saw it in the mirror and, man, I expected the worst when I came back around."
One fan was sent to a local hospital in stable condition, then treated and released.
Daytona president Joie Chitwood said 12 other people were assessed after the accident -- four were treated and released by track medics, and eight declined treatment.
Crew members from various racing teams -- including Earnhardt's -- immediately ran out to the wreckage to check on Dillon's condition and gave a collective thumbs-up to let everybody know that he was OK.
After a few moments, Dillon got out of his car and waved to the crowd. He later said he sustained a bruised tailbone and forearm.
"It is just part of this racing. ... You are praying and hoping you get through it," Dillon said.
Dillon said that type of accident can't be tolerated by the sanctioning body, which, he said, should look at reducing speeds.
"It's not really acceptable, I don't think," Dillon said. "We've got to figure out something. I think our speeds are too high, I really do. I think everybody can get good racing with lower speeds, and we can work on that and then figure out a way to keep cars on the ground.
"That's the next thing. We're fighting hard to make the racing good. I hope fans enjoy all that. We don't. That's your job. You go out there and you hold it wide-open to the end, checkers or wreckers, and hope you make it through."
The wreck started after Denny Hamlin and Kevin Harvick made contact as they crossed the finish line behind Earnhardt, who seemed speechless as he crossed the finish line.
"Oh My God. That looked awful," Earnhardt yelled into his radio. He followed with a string of expletives as he tried to comprehend the frightening accident.
Crew chief Greg Ives immediately radioed his team to not pull Dillon from the car.
"Whoever is in that window, if he's OK, do not touch him. Tell him to stay in there," Ives said.
Hamlin said the wreck started when Harvick gave him a push, a common maneuver at Daytona, and lifted his rear wheels off the ground.
"Just snagged him and turned him as he was in the middle of the track," Harvick said. "I hate that all happened, but just at the end of the race, it becomes pretty aggressive."
Officials with the track and NASCAR said they will evaluate the performance of the catch fence. NASCAR also has taken Dillon's car for a post-accident evaluation, a common procedure after a major accident.
Chitwood said that the new Daytona grandstands cause people to take escalators up to the middle level and walk to the lower-level seats, which eliminates fans from trying to walk next to the fence during a race. He said the fence did its job.
"The catch fence kept [Dillon's] car inside the racetrack," Hamlin said. "I am not sure what else we can really do about it. They are freak incidents that make that happen."
Hamlin said that he likes the current rules package and wasn't sure what changes could be made. His only suggestion was to stop selling tickets at the lower level near the start-finish line.
"You want to make the sport as safe as possible, but we're going to make those mistakes and we're going to make mistakes like that on Lap 1 sometime down the road at a superspeedway," Hamlin said. "Trying to eliminate at the end of the race where it's deciding a winner probably should get played out.
"It's just part of the speed and the cars and the package that we have. I'm happy with the package personally. I believe we have something that races really well, we're running a decent speed -- do we want it to go in the air? No, but it's just going to happen sometimes."
Earnhardt called the crash "terrifying to watch."
"You hate to see that kind of wreck at the end," Earnhardt said. "You are just on the verge of tears. I saw everything in the mirror pretty clearly ... I just was very scared for whoever that car was. I didn't care about anything except figuring out who was OK.
"The racing doesn't matter anymore."
Dillon's brother, Ty, echoed those sentiments on Twitter.
Earnhardt said all he could see was a car up in the air behind him as he crossed the finish line. Dillon said he was just holding on to the wheel.
"It was very vicious," Dillon said. "It's a swishing around in there and the belts are loosening each hit, so the hits are getting more and more violent.
"By the fourth one, you know you've separated enough where your fourth one is going to hurt more than others. But like I said, I held on to the steering wheel as hard as I could."
But it wasn't over when Dillon thought it was. Several seconds after he was sitting there upside-down, Keselowski's car rammed into his. Dillon said Keselowski told him he tried to slow down but must have hit some oil.
"I had already actually relaxed when the 2 [of Keselowski] had hit me because all I can see is the roof and the windshield," Dillon said. "I'm glad we build safe cars at RCR [Richard Childress Racing] and NASCAR."
The Associated Press contributed to this report.
Daytona race ends with scary wreck
Ricky Craven breaks down how no one was seriously hurt after the Coke Zero 400 at Daytona ends with a wreck.
Dale Jr. wins at Daytona, race ends in wreck
Dale Earhardt Jr. wins the Coke Zero 400 at Daytona, which was delayed because of rain and ended at 2:41 a.m. The race finishes with a wreck that had Austin Dillon's car flipped over. Luckily, no one was seriously injured.