Yeah it's probably a boxer's fracture, really common when punching bare knuckle and untrained. He'll probably put your hand in a cast for a couple of weeks. I had one myself (punching concrete wall is bad) and it took about 3 months to heal, but I didn't get a cast put on it so it might be faster if you do.
His helmet was stifling, it narrowed his vision. And he must see far. His shield was heavy. It threw him off balance. And his target is far away.