Black looks necrotic (dead), yellow is chicken pus. If veterinary care is not an option then you'll need to squeeze that pus out while the wound is still open and while you're wearing rubber/nitrile/food-prep gloves as staph infections can be transferred into any cut or open wound you might have on your hands. If you're forced to do this alone, then wrap her from the neck down in a clean terry towel that you don't mind getting stains on. This way you can cradle her like a football in the crook of your elbow on your non-dominant arm and still have both hands available to squeeze out the infection. Don't be alarmed or give up if she resists, both the necrotic tissue and the staph infested pus can cause death if not treated. Rinse the wound after you think you've got all the pus out so you can double check that it's ALL gone, anything left over will fester again and prolong the healing process (forcing you to do the squeezing all over again). Once you're satisfied that all the pus is out and you've removed the black necrotic tissue and rinsed the wound with saline or water (don't use hydrogen peroxide as it's powerful enough to kill living tissue and it stings), lightly cover her eyes and nostrils temporarily so you can spritz her ear with blu-kote antiseptic spray to camouflage the wound from her mates; any color except for red will work fine. Don't bandage the wound. Antibiotics have a chance at working once you've got the pus and dead tissue out of that wound. If the others continue to pick on her and you need to separate her, try to put her isolation pen in the coop where the others can still see and hear her. Out of sight, out of mind with chickens, and if one of their flock members is missing for about a week, their mates forget that they were ever in the flock... making for a rough reintegration. Putting your feathered family in my prayers.
