A sebaceous cyst that has gone pus is not getting better or worse. It is a secondary bacterial infection. Sebaceous cysts themselves are cystic structures formed by blockage of the sebaceous ducts and blockage of sebaceous gland secretions. There is usually no pain or itching, and it may appear as a localized lump. Pus is secondary to bacterial infection formed by the local purulent inflammatory reaction, it is possible that the pus discharge will gradually heal and recover by itself, if you can not heal, you need to take anti-infective measures, such as taking amoxicillin, cefaclor and other antibiotics, pus is more, you should also take a surgical incision and drainage of pus secretions. Sebaceous cysts are pus-filled and need to be treated promptly, under the guidance of the doctor to take appropriate treatment measures.