Bruises on ass - how to hide/explain

So recently I’ve had my first BDSM experience, with a BDSM dominant couple, and I’ll see them regularly as their sub. Two days ago I had a medium spanking, and I still have light/blue-ish bruises on my ass. But, next time we’re thinkg about belt spanking.

So, here’s the problem. I’m 22, living with my parents, and they know nothing about my BDSM preferences, and they re very conservative and I’d have a lot of problems if they found out. Sometimes I walk around in my panties when my mom is home (I feel okey in front of her cause she’s my mother, for example sometimes I ask her if I’ve lost weight, etc., sometimes I try on some new top I bought; it doesn’t happen often but it does happen occassionaly). The bruises I have right now are completely covered by the undies when I wear them, but next time the bruises will be much bigger and I’m worried what to do after that if they end up being visible. I’m trying to come up with stories that I’ll tell my mother if she saw some of the bruises but non of them are goos enough. Please do help me with some tips! Did any of you have a situation when you hade to lie and explain your ass bruises and how did you do that?

And also, it will take me around four days to heal these bruises made just by hand spanking; how long will it take to heal bruises made by belt spanking?