Your hen was probably in some shock, so keep her in a warm place apart from the other chickens. Clean her with warm water and some people use a little liquid soap, but betadine is better if you have it. You can trim the feathers a bit to keep them out of the wound. I use neospirin ointment ( or generic equivalent) for wounds. The ointment, unlike the cream, can be squirted right into the wound. Reapply the ointment every day. Check frequently for the smell of infection. One caution: chickens cannot handle the "caine" drugs that are in a lot of topical meds. This is meds that end in -caine, such as benzocaine, cetacaine, lidocaine, etc.
Chicken can heal from some pretty bad wounds. She may not start eating or drinking right away so make sure she is staying hydrated.
