How can i hide my cuts/grazes from my mom?!

Basically, i've been self harming for years and my mums never noticed, or if she has she never asked whre i got the cuts from or w/e. Recently, i cut four lines into my with my nails (Yes, scratched it in) I also have many of the same kind of grazes on my stomach and same thing again on my bicep in the shape of "Fu" I also have a line i cut with a knife on my left arm. My left arm is also covred in scars.

Anyway after problems with my boyfriends mum, who rang my mum up saying ive had underaged sex, im a stoner and i self harm, my mums most likly going to look for these cuts when im in bed or something or try and walk in on me when im gtting changed or something...

Does anyone know how i can hide them or make them heal overnight??