That's NOT FIGHTING. One or more aggressive birds are PINNING down and thinning the herd. Weaker males give completely up and will sit still while other eat the blood until the injuries become fatal.I
I just put neosporin on it and I have 4 roosters but they never seem to fight each other.
The bird needs isolation for a few days.. kept from FLIES.
You might need to cull it or probably one or 2or all of the males that now are craving blood. Cannibal birds are no fun.
Sad, but the nature of the beast.