I Have Found A Small Lump Of My Anus Between

I have found a small lump of my anus between my cheeks nearest my scrotum. It has appeared over 3 days getting more and more painful. I have had irregular bowel movements that have been painful each time for about a month now. I can't sit on it and it is not piles. It is painful to walk and move. I often feel as I have to poo but regularly no bowel movement. I'm concerned it may be bowel cancer or prostate cancer. Please can u offer any advice? Thank you.