What's this thing in my shamo's cheek?

My shamo mix got in a fight a couple of weeks ago with another male and got his head skinned and he has this weird dark scab/lump/plug looking thin in one side of his face. He generally seems OK, most of his wounds on his face have healed but his behaviour is a bit strange. Hes walking around alright and comes begging for food from us but doesn't really eat much, left to his own devices he doesn't scratch or eat food off the ground. He kind of eats out of the feed bag or when we give him a bowl but sort of pecks without getting much in his mouth, he drinks water OK and we've given him some egg too which he slowly eats. One other thing hes stopped crowing which I've only ever seen with a dying roo.