<s>[INST] On top of my buttocks crack I felt a small ball like lump which hurts when touched. There are no visual sign when looking at the area. It is actually under the skin. The skin is clear.The pain and lump does come and go.I play a lot of sport, but also sit down in the same position for a long period while Im at work.What is the inner lump and why does it occur? [/INST] Hi, Thanks for writing in. A lump in that area can be due to an infection below the skin or a benign tumor. It is best to consult a surgeon and confirm the plane of swelling. If felt necessary an ultrasound scan of the lump may be done, and it will give a confirmation on the location and features of the lump. Infective lumps usually respond to antibiotics and anti-inflammatory medications. Such infections may occur due to sweat in the region infecting the hair follicles in most people. </s>