Apologizing to him, for having him hurt.
If you would have been a minor, you needed to do it with his parents present perhaps also explaining why you did it.
While then the parents may have learned something new about their own child, they also may see from it to take further actions like requesting you to be removed from that university.
As you are, if i remember correctly, over 25(?), dragging you to court could become the bigger issue. If only for money or even to bust your ass.
These things can end very badly and a permanent record is somwthing you may want to avoid. The older you get, the less the courts would see your age as and exuse for anything. Having something in your register, could fuck things up for you in the future even more. Dont take this lightly. It is not "only" a broken nose what could come out of this.