Infante immediately left the game in the seventh inning, walking off under his own power with Royals trainers Nick Kenney and Kyle Turner. Infante, hit in the left cheek, was spitting blood and had blood on his forehead as trainers held a towel to his face.
The Royals said Tuesday that Infante, who was taken to the hospital, suffered a "non-concussive head injury" and that he needed six stitches to close the laceration on the lower left side of his face.
Infante will be evaluated for 48 hours before the Royals decide whether to place him on the disabled list.
"They put a number of stitches in there to close the cut," Royals manager Ned Yost said after Monday's game. "They are going to go scan it and see if his jaw is fractured. We'll know more later. I'm not going to make any decisions (on roster moves) until we find out what's going on with Omar and we'll move forward from there.
"He was bleeding tremendously from the cut. I didn't know until they had taken him upstairs that he got hit on the jaw. When we got there they had the towel (over his head) and there was blood all down his shirt. There was no cut on his forehead that I could see."
Danny Valencia ran for Infante, who signed a $30.25 million, four-year contract with the Royals in December after hitting .318 last season for Detroit.
"He was smoked. We're worried about a concussion, too. It shakes you for sure because it's a very ugly sound for somebody to be hit in the face," Yost said after the game. "It was a cool night, but I noticed I broke out in a sweat real quick, so it definitely affected me. Of course, you have a lot of worry about it."
Bell, who was a teammate of Infante's with the Marlins in 2012, also was worried about Infante's condition after the game.
"My prayers go out to him," Bell told MLB.com. "... I was trying to throw a sinker and just let it run and it ran too much and just didn't finish it. It went up and in. ... I feel really bad. I know he feels bad, but I feel worse.
"You never want to hit anybody like that. Especially a good friend. Before the game, I was saying 'Hi' to him."
Added Yost to MLB.com: "It wasn't as serious as it could have been. But it shakes you for sure because it's a very ugly sound to see somebody get hit in the face."
The Royals won the game, 4-2. The Rays and Royals play again Tuesday and Wednesday.
Information from The Associated Press was used in this report.