I'd suggest a small redraw so her wrist smushes her breast enough to censor the nipple. Honestly, tapas is pretty fine with breasts out without a mature warning, but even they might not approve of it on your icon. Webtoons has shifted to ages v9+ and I'm pretty sure it'll cause trouble there. So definately air on the side of caution with webtoons, but maybe consider it for tapas too, as far as the icon goes.
It's a gorgeous icon, though, which is why I suggest the small redraw. But you can always choose something else, especially if you're only making the change for one site. I know censorship sucks when you know your piece isn't even sexual. You just have to make the best choice you can for you.