Did anyone else have problems with post-treatment canker sores (ulcers) of the mouth? A large one on my lower cheek between my lip and teeth just will not go away and seems to spread. Doctors and dentist have prescribed, acyclovir, nystatin, magic mouth wash, baking sada salt mouth washes. Tried all for over 20 days with little to no change. The doctors and dentist said it is simply an ulcer that will take a long time due to the compromised immune system. Of course I am concerned it may be more serious. Since my original tongue cancer took over 10 years to move from lesions to cancer, I don't want months of this to only find out it is cancer. Anyone have this or a way to treat?