Well, licking it as such wouldn't necessarily cause it to get infected, but the problem is it would keep the wound raw and open. And that way dirt and bacteria would easily find a way in (especially if the dog ran around outside a lot getting muddy) Licking the wound would certainly clean it initially. But if licking continued it would stop a scab forming.
Beyond keeping the wound open, some dogs will get so obsessive about licking the area, they can actually cause a condition known as acral lick dermatitis. This is a non-healing spot, usually on a front leg, that the dog essentially "worries" over constantly.
Where is the wound and what kind of wound is it? Has your veterinarian seen the dog recently?
My dog has a unhealed bite wound on his back he got attacked by a big dog he is only 5 pound:( He has licked off the scab and it's white he won't stop licking it..starting to worry me he just started so maybe he will stop?
OK I think you should take him to the vet.
If he was bitten by a larger dog (and he is so tiny!) -he is bound to have some puncture wounds there.
The thing with puncture wounds is they don't look like great shakes from the surface, but they go deep. There could well be some infection inside. Puncure wounds are notorious for going bad.
White sounds rather like there could be pus in there?
Licking, in this case, may well help to keep the wound open, which may well be exactly what is needed if there is any infection, to allow the infection to drain.
But by far the best plan is to take him to have that wound checked out.