Sores (blisters and ulcers) on the tongue can be caused by
Irritation from certain foods or chemicals
Oral herpes simplex virus infection
Canker sores (recurrent aphthous stomatitis)
Allergies or other immune system disorders
Injury from biting tongue
The side of the tongue may develop a bump into the space between missing teeth. Although small bumps on both sides of the tongue are usually harmless a bump on only one side should be examined to see if it is cancerous.
Unexplained red or white areas sores or lumps (particularly when hard) on the tongue—especially if painless—may be signs of cancer and should be examined by a doctor or dentist. Most oral cancers grow on the sides of the tongue or on the floor of the mouth. Cancer almost never appears on the top of the tongue except when the cancer occurs after untreated syphilis.