Any time there is a sore anywhere on your body that does not get better with time, there is always the concern that there could be a serious cause, such as cancer. It would be important to know more of your history, such as whether or not you have a history of smoking or drinking, as this makes it much more likely that there is a serious underlying cause. Even without those, however, just the fact that it has persisted for so long indicates that you would do well to have the spot biopsied. The fortunate thing is that this can be performed easily in your doctor's office, who can then look at it under a microscope to make sure that there is nothing more aggressive than a normal canker sore that is causing your pain. Things to look out for include increasing pain, increases in the size of the lesion, changes in your voice or speech, pain radiating to other parts of your body, or weight loss (although there are other symptoms, too). Please speak to an doctors
">otolaryngologist, or head and neck surgeon
(ENT), who will best be able to help you determine what is happening inside your mouth.