Brief Answer:
a sebaceous cyst probably

Detailed Answer:
Hello,

although I couldn't make a diagnosis without taking a close look at it, it seems to be one of the following:

- sebaceous cyst: it's a cyst filled with white material; sometimes inflammation occurs and may become painful.
- local infection: a collection of pus under the skin is usually painful, red and swollen. It may be very sensitive to touch.

Your primary care physician, a dermatologist or a general surgeon should all be able to take care of it. If it's a sebaceous cyst then complete excision (including the wall of the cyst) is necessary for permanent cure. If it's an infectious process then drainage is usually the solution. An antibiotic on its own won't be of much help unless the inflammation has spread to adjacent tissues.

I hope I've answered your question. Please let me know if you need further assistance.

Kind Regards,
Dr Panagiotis Zografakis,
Internal Medicine Specialist

---