its funny you should ask bc i also had to look it up when i saw it in art. apparently he has a surgery scar on his stomach from when he was a kid. we've never actually seen it afaik, i dont think he talks abt it v much but ive seen ppl say he's mentioned it being an insecurity, so he doesn't wear outfits that show his abs etc. ive also seen ppl call it an appendix scar but idk if that's confirmed. theres not a lot of info bc it seems p private to him so take all this with a grain of salt lol