
Hi Dan, are you talking about the slightly different coloured patch diagonally opposite your finger knuckle?
If it is, and given the history you state this would not appear to be an issue of concern. Like patches of skin elsewhere across the human body, pigmentation change can occur at any time - and become permanent. Obviously, that may not be what it actually is - so it is trying to come up with an explanation for it! I don’t suppose you Guy’s (you and your partner) are into rough sex games or masochistic stuff?
You could have a skin condition developing: this is of course a potential explanation, particularly if you have a skin condition such as psoriasis and suchlike elsewhere on the body.
If non of these suggestions ‘fit’ or make sense, I think what I would perhaps do is try yo even-out the impact of what you have here - and of course, only use a healthy option. If this was me I would try a light application of liquid Coconut Oil 2 or 3 times a week - particularly after you have taken a shower.
Other than that, I would keep a close eye on it to see if anything else develops …