I have a 2cm red/white mouth sore under the top lip and can be painful more after eating, do i need a dentist or doctor. had it for 2 months please

Oral surgeon: If you see your dentist, he/she will refer you to an oral surgeon. If you see your MD, he/she will refer you to an ENT doc. I would recommend seeing an oral surgeon first. Oral surgeons see far more of these things than any other doc. Expect a biopsy to diagnose lesion.

The rule of thumb: If you have an ulcer that's increasing in size and/or it's been there for more than two weeks, see your doctor or dentist for evaluation.

Mouth sore: You should definitely start off by seeing a dentist. Since you gave us very little to work with, it's hard to determine the cause. It could be an infection from a tooth or gums, denture sore if you wear any removable appliance, a symptom related to a medical issue, or any number of different types of lesions. If your GD can't determine the cause\treat you, he\she may refer you to Oral Surgeon\MD