Lump below scrotum

Hi there!!

I could see a small hard lump below the scrotum and above the anus opening.

It comes and goes few months.

Basically, I was feeling around and I noticed this very small and hard (almost like a baby marble) near my anal opening. Its located slightly towards my left sid side of anus. Probably a half inch from the anal opening.

But its not external. I have to push my skin in a little to actually feel it, and I do get slight pain when I do this. But it usually goes away after few weeks. I feel pain when u press it.

Kindly help.