Hello,
The following are few probable causes of yellowish skin lesion on buttocks:
1) Boil or furuncle
2) Carbuncle
3) Ulcer
4) Sebaceous cyst
5) Fistula
You need to be clinically examined in person. To those who come to my clinic with similar symptoms, I advise the following:
1) If pain exists, you may use over the counter pain relievers like tab.
ibuprofen or tab.
Naproxen twice daily.
2) Topical ointment can be applied like
mupirocin daily twice.
3) As it is yellowish, it might be infected. So, antibiotic can be started like tab.
amoxicillin clavulanate 500mg thrice daily for 7 days.
4) To prevent gastric irritation, tab. Pantop is to be taken before food.
If symptoms don't subside even after above treatment, you may need to consult a physician in person.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Pallavi M., Anesthesiologist