Answers:
It might be an abscess, or a pylonidal cyst [like an ingrown pelt but larger]. If the nouns appears red and reheat to the touch it might be infected and the soul must see a doctor for treatment [antibiotics and drainage of the abscess/cyst]. If no signs of infection are present, thaw compresses or a heat wipe, and scrub the nouns beside an exfoliant [like the ones used for the obverse; I'd recommend St Ives Medicated apricot scrub because it contains salicylic acid], will engender the cyst interested and drain w/o medical intervention in a few days.
Sounds resembling a sebacious cist; can be found surrounded by most form related, or home form manual.
This one would mull over that the personage next to the mass wishes to be in motion and get hold of a medical belief as soon as possible.
It is substantial to address problems contained by the body until that time they achieve a stage that can produce problems. I enjoy hear horrible stories where on earth population have a form problem and didn't detail any one, some died.
It probably a pilonidal cyst, it requirements to be drained and the character put on antibiotics.