What is the hard,purple bump on my butt?
Patient: There is a bruise like mark on my butt cheek, basically on the crack line. It's been there for over a year and  from time to time it hurts. You can feel a little bump if you touch it and it's very visible. Purple. It feels tougher than the rest of my butt. Help! Doctor: Hi,This may be a pilonidal sinus. I suggest you see your doctor for assessment. This is not a serious problem but can be helped by surgical removal to prevent any infection developing. Regards,Dr K A Pottinger