A clinical examination is necessary to confirm the cause. Inflamed papillae can sometimes cause small, painful bumps on the top surface or upper sides of your tongue. Tongue sores are usually caused by trauma, physical injury, bacterial or viral infections, vitamin deficiencies and tonsillitis. If sores are large, painful, or persistent, it is best to consult a doctor. It is best to avoid citrus fruits and acidic vegetables and spicy foods till it is cured. The other causes for pain could be GERD (Gastro Esophageal Reflux Disease), where the acid contents of the stomach came up into the esophagus and peptic ulcer disease. Consult your attending doctor and clarify your concerns if these drugs are causing these symptoms. See a physician.
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Yes, i would also recommend you to undergo a proper dental checkup before coming to any kind of consent.
If it's going away on it's own it's probably not cancer, but whenever you have an unusual growth in your mouth you should have it checked by a dentist.
I would also suggested you to go a proper dental test before coming to any kind of clearance.