A bump on the buttocks that hurts is most likely due to a boil. Boils are common bacterial skin diseases in dermatology. The main causative agent is Staphylococcus aureus, and they occur in all parts of the body. Clinically, the rash mainly presents as localized inflammatory hard nodules with increased skin temperature and positive pressure pain. When the above symptoms appear, you should actively go to the hospital, do not squeeze or scratch to stimulate the infection may lead to further spread. If the symptoms are mild, you should give a topical treatment with chlortetracycline ointment or Bactrim ointment or compound polymyxin B ointment. If the rash is large and the infection is severe, the patient should be advised to systematically take oral or intravenous antibiotics to control the infection, and after the symptoms have improved, then local incision and drainage treatment should be performed.