Welcome and thanks for posting your query to HealthcareMagic.
As per your query you you have red bumps on butt crack, itchy, tender and is growing in size.
The characteristic feature appears to be problem of cyst
with pus collection. It is quite common to find these kind of cyst at this area because of bacterial infection.
You should meet a surgeon at the earliest other wise the cyst can grow into larger size and may then need incision and drainage
. Till that time do not scratch or even try to touch the area unnecessarily, apply any antibacterial cream such as fucidin
2 times a day in a very thin layer so that it should not be visible to naked eye.
I hope these information's will help you. If you have further queries I will be happy to help.
"Wish you good health"
Dr Sanjay Kumar Kanodia
MD (Dermatology and Sexually Transmitted Diseases)