I had an injured hen from a coon attack. She was missing an area on her back about 2"x3". I brought her in the house and cleaned out her wound, gave her antibiotics, kept the wound moistened with triple antibiotic ointment. It scabbed over and she was back with the others in about 2 weeks. Now you can't even tell she had a wound.
I'm thinking alot of what I did was inconsequential. What I mean is, chickens have an incredible ability to heal. I'm thinking she would have probably healed even without my help!
I think the best thing you can do is keep the flies away from it. That's why I brought my hen into the house, otherwise I would just have tended to her in a crate in the coop.
Good luck to you! You're doing great!