Our other dog (seen pictured at left) burst a disc and was paralyzed in March. He had surgery and is back walking like a drunken sailor. BUT, shortly after the surgery he started licking his back left paw and then, when we were gone, he knawed part of it off!
The scene was like something out of The Texas Chainsaw Massacre.
The vet said his paw probably hurt him or was numb from his back problem. He had to wear a "lampshade" for a few months (still wears one when not supervised).
Vet said licking can be signs of pain or other neurological issues.
Read more about licking