Getting the wound clean is very important. After one of my hens survived a fox attack, my vet told me that the good news is that chickens can't get rabies, but that with bite wounds you have to really be on guard against infection because either a claw or a tooth can penetrate pretty deeply.Ok we will cut it down tomorrow. We bought an anti microbial spray and sprayed the area but not actually cleaned with soap and water .
With deep injuries, you can even use a syringe to really spray a hard stream so that it pushes the liquid into the wound and not just on the surface. (Don't put the syringe into the wound, just use the syringe to generate a stream of water with some force).
If you have any access to a vet, you might be able to get some antibiotics or at the very least something anti-inflammatory.