I still think he most likely got in a fight but that is what they do. They are most likely to hurt their spurs or get pecked on the wattles or comb but they heal very fast in these places too. I would check to see he can't hurt himself on anything sharp but it probably was a fight which is to be expected, they have to work out who is in charge. I know how worried I was when my guy hurt himself but eventually I got used to him having blood in his face. He was a tough little buff sussex, your reminds me a bit of him. Isolating things will just make things worse, if they are to be kept together, keep them together, a little bit of blood is no reason to seperate them, that will just make any susbsequent fight worse. You want them to fight, get it over with and move on.