You don't say how old your dog is. I had scotties some years ago, and when they were getting old some of them had black growths on their lips, though not as big as a pea. The vet said they were warts, and harmless, though to keep an eye on them in case they got large.
If your dog is insured, do they have a helpline? Worth checking for peace of mind. I would take a photo every couple of weeks to monitor size and check if it grows quickly.
Hope this helps.
Lesley
