Flesh lump pain in the inside of the mouth is considered to be caused by mucus cysts, oral ulcers, and fibrous tissue hyperplasia. 1. Mucus cyst: mucus cyst refers to the mucus glands due to injury or lesions lead to mucus can not be normally discharged from the body, and retained in the oral cavity to form cysts. Mucous cysts can be triggered by not paying attention to oral hygiene and injuries to the cheeks. 2. Mouth ulcers: Stress and poor diet can cause mouth ulcers, which are yellowish-white herpes with painful symptoms. Difficulty in opening the mouth, which interferes with eating, may also occur. 3. Fibrous tissue hyperplasia: patients with fibrous hyperplasia inside the mouth, may form tumor-like lumps, muscle strain or local inflammation inside the mouth can lead to fibrous tissue hyperplasia. Patients should pay attention to oral hygiene, pay attention to diet, drink more water. It is recommended that patients go to the stomatology department of the hospital for the corresponding examination, and the doctor will carry out the corresponding treatment according to the specific conditions.