In addition to these, some other important causes are, viral or bacterial infections, cold sores, nutritional deficiencies, especially the deficiency of vitamin B12, iron, and folic acid, hormonal fluctuations, smoking, excessive use of alcohol, and tuberculosis. Tongue sores are usually not cancerous, especially if they are painful. Cancerous sores or bumps appear on one side of the tongue, and they are painless and hard to touch.