Thanks for writing.
Yes, you seem to have developed an ulcer/blister
. The duration of recovery depend on the severity of ulcer. Perhaps it may take another week to improve. That being said without an opportunity to examine the blister it is difficult to understand the seriousness of the condition. Therefore I encourage you to consult your doctor and get it evaluated.
In the interim avoid hot and spicy food. If the blister is accessible, you can apply oral paints/gels/glycerine. Vitamin (b complex and c) supplements can be helpful.
Wish you good health.