Despite the romanticism surrounding the emotion, it can be difficult to be loved completely — not just the beautiful parts of us, but also the sad parts, the injured parts, the hidden and less-than-pleasant parts. There are marks on us, both physical and mental, that we'd often rather forget. The mental ones can just be easier to hide. As for physical scars, they can be off of our minds some of the time, but that's exceedingly hard to do in more intimate, close moments.
Whether it's to your dismay or otherwise, your partner is not looking away and ignoring your scars. To the contrary, they're providing attention in a way most heavily associated with tenderness: kissing. It may be an accidental slip off target, or they may be trying to show you that what you've done and who you've been don't matter to them now.
Does the gesture touch you? Make the walls come up once again because of the memories that are dredged from somewhere you'd rather no go? A mixture of both?
The wound has long closed, yet the pains remains; these days, however, there's someone who may be willing to help you bear it.
Reply with the usual: canon, character, preferences, et al. You may also want to say if you're down for smut or not, since it's not a given.
Be sure to include what side you'd like your character to play. Mention if you can do both the kisser and the kissed.
Also, feel free to talk about your character's scars.