I don't think it would be an issue. The number of trans guys on here that have a history of self harm is pretty crazy, so I'm sure they'll have seen it all before (I'm assuming that this is a trans related surgery, ignore this if it's not.) It's not their place to decide who can and who can't have the surgery, it's their place to cut you open and do what needs doing.
I've got some fairly noticeable scars on my arms, they've faded a bit these days I think, but when I had a minor operation it had only been a few months since I stopped if I can remember rightly. No one mentioned anything if they even noticed. Actually, since leaving the school that everyone knew in two years ago, it's only been pointed out to me that people noticed in this last week. And that's because we've been talking about self harm. If you don't draw attention to thing people don't make that big a deal out of them.