Hello,
It looks like pilonidal cyst to me. It is a cyst right over the coccyx area. In this the skin becomes reddened or even sometimes looks like a small bruise. When it is infected, it causes pain and discharge .Antibiotics or surgical drainage may be required in such cases. Please consult a surgeon and get it evaluated.
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.
Try a treatment for dhobi Itch/Jock Itch. It's like athlete's foot but in your butt crack, nice.