Many people first notice oral cavity cancer as a stubborn mouth sore or ulcer that doesn’t heal after 2–3 weeks, sometimes with a thickened patch, a red or white spot, or a lump on the tongue, gums, inner cheek, or floor of the mouth. You might also pick up warning signs like unexplained mouth pain, a feeling that something is stuck, bleeding, loosening teeth, difficulty chewing or speaking, or a new hoarseness; some notice numbness or a change in how dentures fit. If a sore persists, especially with risk factors like tobacco, heavy alcohol use, or HPV, that’s the moment to see a clinician or dentist to check whether these are first signs of oral cavity cancer.