Sometimes it's just the scab with nothing underneath.
I would apply antibiotic and keep it wrapped for 4-5 days to keep it clean. The hen I had was limping and it was really obvious. Another had black spots on her feet but she seems fine and I have left her alone. I am beginning to suspect that many chickens get it and owners don't know it unless the bird starts limping or they are looking for it. So, it's possible that many birds get over it on their own. Could be wishful thinking on my part.