There are two things you can do. One of which is rat him out. Sure you may be a social out cast but you did the right thing. Or you can let it be, and if it continues he may have the same thing happen to him that happened to a Sgt Maj and a Lt my dad was under in the Royal Army. They turned around really fast.
The Sgt Maj wasn't harmed physically. But the LTs example was, "Those under you can project your butt or put a bullet in it."