As others have said, it could be dog earring. I did have slight ones, but theyve gone down and arent noticeable now (working out really helped contribute to this by building up that area).
But also one thing I noticed, though it may be different to what youre experiencing, was a hard lump where the drain had been taken out (as opposed to below, like you said). It felt like a large and firm spot/pimple whatever you want to call it.
But...*just having a feel of that area now*.... I can only feel a tiny dot at most now. Im guessing it was the drain hole wound healing and scarring that I could feel. Maybe it is that...?