A bump inside the upper lip could indicate a canker sore or a cyst, also known as mucocele, has developed. A mucocele develops on a small salivary gland and forms a white bump on the inside of the lips that is typically painless, according to WebMD.
Bumps inside the upper lip can also be caused by injury if the mouth area is jarred. The most common cause is a mild infection within the mouth, explains MedlinePlus. Canker sores typically develop in conjunction with viral infections and are considered a form of mouth ulcer, indicating problems within the body's immune system. Canker sores can also develop when the teeth are cleaned roughly, the mouth is injured from dental work or a person bites his tongue, cheek or portions of the lip. Bumps on the lip can also be caused by stress, a lack of vitamins in the diet, hormonal changes or food allergies.
Treatment for canker sores and small cysts on the upper lip is often rest and time as these sores naturally resolve, notes MedlinePlus. If the cysts, bumps or sores become painful and interfere with talking or eating, physicians may recommend over-the-counter pain medications and antibacterial mouthwashes to minimize the growth and soreness of the bumps.