Painful lumps under the buttocks can be caused by boils, perianal abscesses, hemorrhoids and so on. 1. Boils: due to purulent infection of hair follicles and deep tissues, early inflammation will cause subcutaneous nodules, redness, swelling, pain and other symptoms, so it will be manifested as a lump pain under the buttocks. 2. Perianal abscess: purulent infection of the soft tissues around the anus or the interstitial space, which can also lead to the symptom of painful lumps under the buttocks. 3. hemorrhoids: hemorrhoids caused by poor circulation around the anus may also lead to a lump under the buttocks, pain, and some may also cause blood in the stool and other manifestations. There may be other reasons for the lumps and pain under the buttocks, you need to go to the hospital in time for examination, and follow the doctor’s instructions for treatment.