Hi there. I think you have discovered your sacral dimple. Lots of us have them and dont even know. However if it starts to leak fluid or become painful or the skin breaks open then thats a different matter.....it could be the start of a pilonidal sinus and as such you will need a doctors attention. Its nothing to do with STDs but they do need medical attention.
and how about the kind of over skin in the hole like ...?
do you think the "kind of skins" there in the anus can be an STD ?
what is this kind of skins ?
Those lumpy bits are skin tags and are quite common. Nothing to do with STDs. If they dont normally bother you then leave them alone.If they become a nuisance you need to see your doctor so that they can be assessed and possibly removed.