I agree - it sounds like your Pekingese needs a really thorough oral exam, which may need to be done under sedation. Severe dental disease, gingivitis, or even an oral cancer can cause this, so I'd get it examined carefully (or even biopsied) as soon as possible!
I think I would have this spot re-examined by your veterinarian again. While it may have looked one way 10 months ago, it could look like an ulcer or eroded spot today and may be a good candidate for some sort of treatment. Your veterinarian would know best what to do with this as we cannot see it.
There are methods for cauterization or another type of local / topical treatment.