LeBron James says emotions got the best of him after the tough Game 1 loss and his frustrations caused him to injure his hand. (0:44)

CLEVELAND -- Cavaliers star LeBron James played the last three games of the NBA Finals with a significant and "self-inflicted" right hand injury that he suffered following the team's Game 1 overtime loss.

Sources told ESPN that the injury was the result of James' punching a whiteboard in the locker room after that game. James was frustrated by the overturned offensive foul on the Golden State Warriors' Kevin Durant with less than a minute remaining in regulation, which was changed to a blocking foul on James following a replay review by the official, and not JR Smith's lack of recognition in the final seconds, sources said.

"I let the emotions get the best of me and pretty much played the last three games with a broken hand," James said following Friday's Game 4 loss to the Warriors.

James had two MRIs during the series and wore a soft cast when he wasn't practicing, playing or in view of the media, sources said, so as not to give the Warriors a competitive advantage. He iced the hand after games and used a tennis ball to strengthen his grip and try to push out the swelling on off days, sources said.

He appeared with a cast on during his news conference after Friday's game.

play 1:25 LeBron punched blackboard after Game 1 Brian Windhorst explains that LeBron James fought through a right hand injury in the NBA Finals after punching a blackboard after Game 1.

James scored 51 points in Game 1, going 7-of-16 from the field on shots from 10 feet and out. He struggled shooting from such distances in the remaining three games, going a collective 5-of-19. His average shot distance, meanwhile, went from 12.6 feet in Game 1 to 10 feet in Game 2, 9 feet in Game 3 and 4.7 feet in Game 4, according to ESPN Stats & Information.

James described that Game 1 loss as "very emotional" for him.

"For a lot of different reasons," he said. "Understanding how important a game is on the road for our ball club, what [winning it] would have done for us. The way we played, the calls that were made throughout the course of that game, and I had emotions that the game was taken away from us. I had emotions that you just don't get an opportunity like this on the road against Golden State to be able to get a Game 1."

James finished the Finals with averages of 34 points on 52.7 percent shooting overall (33.3 percent from 3), 10 assists and 8.5 rebounds.