Well, if they are still alive the pain reliever didn't seem to damage them. Many chickens can survive some awful wounds, and this picture doesn't look like there is infection. I would probably not use peroxide more than once or twice since it may prevent healing, but betadine or chlorhexadene are good, and some just use soap or saline. Plain Neosporin or Triple Antibiotic ointment is good. These things take awhile to heal over a couple of weeks. Keep flies away to prevent maggot infestation, and give them a little extra protein in some egg or canned tuna to promote healing.
It was infested when I first saw it. It has eaten a hole in her leg bone and she waa unable to stand. She is now standing on one leg. Bathing and caring for these hens is how I noticed the red rash and found the mites. Oh my goodness, now I am about to treat them with 7 dust. TG for this web page.