What is "wrong" with that dog is commonly known as "food aggression". Basically it means he will attack anything that comes near his food. In this case it's his own paw... it could just as easily have been a small child...
Not good. not funny.
Tony
Tell me about it...
I have the same affliction, although it is commonly known as "beer aggression". I got a black eye, and 7 stitches when I accidentally got too close to my cooler, and saw myself reaching in....