Summarize:

If any signs or symptoms last for more than two weeks or quickly get worse, then contact your doctor or dentist as soon as you can. Unless your family physician is also an ear, nose, mouth specialist (otolaryngologist), then your dentist may be the better bet to start with because they can rule out any non-cancerous mouth problems more readily and then treat them to relieve your discomfort.  In addition to a mouth exam (including your lips, cheeks, tongue, gums, tonsils and throat) your neck, ears, and nose should also be looked at to determine the cause of your problem. Your doctor or dentist will also ask you about risky behaviors (tobacco smoking and alcohol use) and your family history, as some cancers have a genetic link. Be aware that people over 40 years of age, especially if they are male and of African American descent, are considered at higher risk for oral cancers. Along with an exam of your mouth and throat, some dentists or doctors may use special oral dyes to better visualize abnormal areas in your mouth, especially if you are considered at higher risk for oral cancer. For example, one method uses a dye called toluidine blue.  Putting toluidine blue dye over a cancerous area in your mouth will make the diseased tissue stain a darker blue than surrounding healthy tissue. Sometimes infected or injured tissue also stains dark blue, so it's not a definitive test for cancer, just a visual guide. To be sure of cancer, a tissue sample (biopsy) needs to be taken and looked at under a microscope by a cancer specialist. This way you can get an accurate diagnosis. Another method of trying to distinguish healthy tissue from cancerous tissue in the mouth is by using special lasers. In general, when laser light is reflected off abnormal tissue, it looks different (duller) from light reflected off normal tissue. Another method uses a special fluorescent light to view the mouth after it's been rinsed with an acetic acid solution (vinegar, basically). Again the cancerous tissue stands out.  If an abnormal area of the mouth is suspected, a tissue biopsy is usually performed. Alternatively, sometimes the abnormal tissue can be evaluated by exfoliative cytology, where the suspected lesion is scraped with a stiff brush and the cells looked at microscopically.
Make an appointment with your doctor or dentist. Ask your doctor about special dyes for your mouth. Ask your doctor about using laser light instead.