That sounds like the sores I get from Crohn's. Mine have a white center and hurt pretty bad, depending on where they are. I have had them on my tongue, the inside of my cheeks, the roof of my mouth...they are not fun. Mine seem to come on at the very start of a flare. They have not been as bad since I started on Pentasa and I am hoping the Remicade keeps them away.
When they were really bad, I would put Kanka on them. It helped but numbs everything else up in the process!