Kitten dry nursing HIMSELF-normal or no?

Got a male kitten about one week ago, but he is two months old. He dry nurses nothing else but himself. He purrs while doing so and does the kneading thing with his paws, so that indicates he's not hurting himself, right? I haven't had a cat since I was very young and not sure what to make of this. Should I make him stop, if so how? Thanks guys.