The old man and the dog

An old man came out to smoke his pipe and there was a dog in his back yard. A guy walking by stopped and asked the old man, “Does your dog bite?” The old man replied, “Nope.” So the guy goes over to pet the dog and when he does the dog bites him in the hand and the guy is screaming and moving around and he asks the old man, “I thought you said your dog doesnt bite!?” The old man replied, “Aint my dog.”