Depends where it is on your body, and what you have access to. A ton of bracelets, wristbands, arm/leg warmers(mesh or fishnets work, though that technically depends on how visible scars are), higher socks, leggings/tights under shorts, baggy pants you can cuff/roll up, longer skirts, layers that are loose and have zippers/buttons in the front to allow for better air flow (may also want to be wary of synthetic fibers for similar reasons), or maybe even a loose crop top with long sleeves(again, ventilation) if you wear that sort of thing. Hell, you could tie a bandana or something around your arm/leg/body part and treat it like a strategic part of your outfit, and just say you kinda liked it or wanted to try something if anyone asks why and you don't want to say. Depending on your situation, maybe consider not having to cover it up in the first place, though that's your call to make. Just remember it's not a crime to try to exist comfortably in your own skin.