Welcome to Health care magic.
1.The most possible cause of the lump is hair follicular infection (
carbuncle /
furuncle) with pus with in.
2.The lump is painful means its infective process.
3.I would suggest you to see your GP, let the lump get examined and treated accordingly.
4.If its small enough - a course of antibiotics will help. If large - a small
incision and drainage followed by antibiotic treatment might be needed.
5.The lump/lesion in the tail bone - has quite a few complications and may form
sinus, fistulous opening to the
rectum.
6.Do not ignore, heel local hygiene , do not scratch, compress the lesion as it will complicate and delay healing process. Good luck.
Hope it helps you. Wish you a good health.
Anything to ask ? do not hesitate. Thank you.