What could I use to stop dog licking paw?

So my mini schnauzer is currently getting over a lick granuloma. We think he got something in his paw that irritated it and he licked it until it was a welt. We had a friend who works for the bluecross check it out and she said to wash it with an antiseptic spray and use a cone to keep him from licking. Issue is, it's now almost totally healed and he's still trying to lick it. So I'm looking for something that'd deter him.

I washed the paw with some diluted apple cider vinegar, cause I heard that's good for soothing wounds, but it seems he doesn't mind the taste, as he's still trying to get at the paw. I'm not sure if there's anything else I could use?

Also as an extra question. I heard just recently that teatree oil is very toxic to dogs? We'd been mixing a drop into their washing mixture to help sooth his skin, as that's what the breeder said they did. We trusted them as they'd been long time krufts breeders, and our vet said it wouldn't be a problem as it was so diluted.

I'm assuming my vet knows what they're talking about, as several well regarded dog shampoos have teatree oil in them. I just wonder how little is in those shampoo brands vs what we use. We're going to stop using it in the future just to be sure, but they've not had any issues from it so far thankfully.