You may want to get a picture to post her and start another thread of your own here for more help:
https://www.backyardchickens.com/forums/emergencies-diseases-injuries-and-cures.10/post-thread
@TL003 could you post any pictures of the lesion on the back and possibly start a new thread, since this one is 7 years old. That would get you more looks and advice. Start a new thread here by clicking here...
I would at least place him in a pen or large crate with his own food and water. Disinfect their water and feed containers. That does look like canker to me, but I am not a vet. Do you have a vet who would see him? I would try to get it diagnosed to make sure it is not something else. An avian...
Welcome to BYC. It looks like one of the common beak bumps that many people here ask about. The first thought is it could be a papilloma from a virus that may fall off eventually, or a cyst. Some chickens can get an injury from a sharp feeder or piece of fencing. I would just watch it to see if...