I had a similar thing happen once. I went to the dr. and they said it was thrush - yeast infection in my mouth....YICK! Anyway, they put me on antibiotics and it cleared up..
Hope that helps
My husband had something like this come up. it turned into a pretty large sore in the roof of his mouth. It bothered him to the point he couldn't eat. It also started to peel. I guess he had it for a week before going to the Dr which didn't give him an explanation of how it came about but gave him some medicine that cured it. I beleve he has had a smaller since then. (within 3 years)
So, from my experience you could see results within a couple of days after seeing the Dr. Good luck. Wish I could tell you more.