How To Get Rid Of Lump On The Anal Opening?

I have a small hard pink coloured lump on the entry to my anus, it is not usually painful, although I do sometimes experience pain when passing stools - it is about 2-3mm long and 2mm in diameter. I think I have had it for the majority of my life, also I have never had sex so I doubt it isn t any kind of STI. Hope you can help and tell me what I can do to get rid of it. Thanks!