What Causes Dark Circles Around Anal Opening And Between Buttock Cheeks?

I saw a doctor about anal itch which i thought was hemaroids but was going on for too long even after using cream.. When applying the cream i noticed a large dark circle around the entrance to my anus, more so on the inner skin of my butt cheeks thought this has never been itchy or sore etc. i was prescribed anti worming treatments and anti fungul creams and informed it should pass within 5 days. The dark circle does not seem to be fading so im concerned this isnt the issue. Thoughts?