Thanks wyrop that was the one I was thinking but after long night of pain brain isn't working wellHe is probably going to be sore for a few days.
Provide him with a deeper dish to drink out of. He may not eat for a day or so but I would make a wet mash of feed for him (feed+water to the consistency of oatmeal) so he's not trying to "pick" at pellets or crumbles.
Check him for any other injures around the head/neck that may be hidden by feathers. If you find any, clean them and apply triple antibiotic ointment.
Barring that he has no other seriously injuries, I think he should be fine.
Roosters can get along until they just don't. You will probably have to keep them separated from now on.
One of the best examples on BYC of how well a chicken can heal and their resilience is Miss Fluffy Bum - she did have a long way to go there at the beginning and she recieved great care from her owner. Fluffy Bum survived and thrived, so take a moment to look through some of the photos at the beginning, then the last few pages which were 3 yrs later https://www.backyardchickens.com/threads/plese-help-chickens-beak-got-bit-off.848424/