Blue circle under skin, now infected?

For awhile I have had a tiny blue circle under my skin. It is located in a stretch mark on my lower abdomen near the top of my leg. It was a solid thing that could kind of move around under the skin. I read another post where someone described it like a tiny rubber band under the skin. It was just like that. I wasn't concerned about it before, but last night noticed it and the skin around it had become pink and puffy. The area where the circle is sticks out a little more and is also kind of yellowish like pus is under the skin. Kind of looks gross like it might come to a head. A little tender where the seam of my underwear rubs against it. Anyone have any ideas what it could be? Thanks!

[Bhupinder Kaur, MD]

Hello,
From the symptoms it can be a hematoma with an infection or a boil. Keep the area clean and apply some topical antiseptics. Also wear loose-fitting cotton clothing and use an antibacterial soap or mild soap like dove. Avoid any kind of cosmetics. Topical antibiotics such as mupirocin or neomycin containing ointment are also useful. Also please consult a dermatologist as you may need oral antibiotics and maybe incision and drainage.

It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.