Following an early afternoon shootaround ahead of Wednesday night's Game 5, Stephenson said he and teammate Paul George both said things they shouldn't have.
"I think this stuff bothered us a little bit," Stephenson told reporters.
"It's part of the game. I think I said some things that shouldn't have been said. Also Paul. We just gotta play basketball and stop worrying about all the other stuff."
The Heat lead the Eastern Conference finals 3-1 and can clinch a spot in the NBA Finals for a fourth straight season with a win Wednesday.
NBA officials fined George href="http://espn.go.com/nba/playoffs/2014/story/_/id/10991917/2014-nba-playoffs-paul-george-indiana-pacers-fined-25k-comments"5,000 for criticizing the officiating in Game 4. George said he expected the fine after complaining about "home cooking" and saying the Pacers "outplayed" the Heat everywhere except the free throw line during Monday night's 102-90 loss in Miami.
"I knew I was going to get fined," George told reporters Wednesday. "I was just speaking my mind. It's just how I felt the game was going."
Stephenson faced the most scrutiny after suggesting before Game 4 that LeBron James' trash talk on the floor was a "sign of weakness."
Stephenson said he should have kept his thoughts private, and he called it a learning experience.
"I been learning since I got in the league," he said. "I came a long way. And I'm gonna keep learning 'til I get to that point where I'm a real pro."
The Associated Press contributed to this report.