How can I stop my dog from biting?

I'm really worried about him, he's done this before and I don't know how to fix it. He's been biting his hind leg and licking at it and now the skin is all red and such. I think i recall reading somewhere that you can put vinegar on it to make him not want to touch it, but I'm not sure if it will sting his skin, I don't want to try anything until I'm sure.

maybe a vet?

You can try the vinegar, a vet, or try garlic powder but not salt. you have to put something he doesn't like or wouldn't want to eat. HOPE THIS HELPS! <:O)