Could this be dry skin or something else?

  Last year around September my puppy dog very quickly and excitedly ran out of his cage (don't put him in it any more), didn't clear the corner, and subsequently ripped one of his toenails clean off. I took him to the vet and got it all fixed up, but now he seems to be bothered by it, like it's itching him or something. He won't let me go near it, so I took him to the vet couple months ago about it, and they said it was fine. However, he still seems bothered by it somehow, won't even let me touch his little paw. Has anyone else experienced something like this with their dog? Thanks.
It s sometimes called 'memory pain' ..... something similar to you cutting your nail too short and being very careful about how you cut the next time .... a dog is not a logical as a human and a dog doesn't understand as much.