Have you ever played a sport, sometimes tempers flare especially when you are playing with grown men.
Probably did not punch correctly. Looked like he made contact with the ring and pinkie fingers on the punch instead of the forefinger and middle finger. Those two fingers are more supported by he wrist and elbow and have better shock absorption. There is not much behind the pinkie or ring finger and I have seen guys hurt themselves but contacting with that area. It was not that good of a punch, looking at the play, he had every right because that guy gave him a doozy of a cheap shot.