SO IT WAS REALLY A MATTER OF TIME BEFORE HICCUP GOT SCARS.
He’s not canon Hiccup. He’s actually from a modern verse of mine where he’s got dragon’s blood in him. The scars are from about a month of capture, where he was chained down in dragon form and more or less left to die. There were shackles around his arms, legs, wings and neck, and three magical spears driving into his back to kill him all dead and stuff. The scars transferred over to his human form and he’ll never be able to get rid of them.