A fleshy pimple inside the lips may be due to the following reasons: 1. It may be a sebaceous cyst on the lips, which may cause slight pain when pressed, and can usually be surgically removed or left untreated. 2. It may be a cyst or trauma scar on the mucous glands of the lips, which may be caused by bad habits of lip biting, and can also be surgically removed, and the bad habits should be corrected. 3. It is possible to have herpes of the lip, and herpes is usually caused by herpes simplex virus, you can carry out antiviral treatment, commonly used are acyclovir, valacyclovir, ganciclovir, or choose ribavirin is also known as virazole, it is recommended to maintain oral hygiene and often use mouthwash, such as compound chlorhexidine rinse.