He's had some little black spots since he was a tiny roo but these are new at the back end are all new as is the discoloration and bleeding. It seems to cause him no pain.
Haven't got a clue but googled it out off curiosity and it said it could be comb scab , it's where another chicken has pecked it leading to a fungus didn't seem to see a cure but hope all is well x
It looks like a pecking injury or dry fowl pox. Pecking injuries in my rooster took almost 3 weeks to heal. Fowl pox comes from mosquito bites and it not a big deal unless you get wet fowl pox inside the mouth, nose, and eyes--then it is very serious. There is no treatment for dry pox.