Maybe allergies? My pointer used to lick/chew at her feet all the time. My husband had read in a gun dog magazine that this can be a sign of allergies. When we went to the vet for another injury, the vet gave us medicine for the injury. He said if the foot licking/chewing was allergies, this medicine would probably work on it also. From the first dose of medicine, she has stopped the behavior. Interestingly, the vet told us that this behavior is from inhaled allergies versus a contact irritation to the feet. Weird. I just thought it was nervous energy because she is such a high energy breed.