My mom walked in on me changing and saw whipping marks on my back, now I don’t know how to proceed

I’ve (22F) been in a relationship with Mark (27M) for around three months. We were friends for a few years before dating each other (we also had on-and-off no-strings-attached encounters over the years as well).

Mark is into domination, I am into pain, we get turned on by these extreme acts of intimacy so of course our chemistry in bed is off the charts, and chalk that in with the fact we know each other extremely well, it really helps.

I stayed over at his place for the weekend and he whipped me, and I thoroughly enjoyed the experience.

I am into feeling the after-effects of the whipping as well because it doesn’t just last when I’m being hit but afterwards there’s a certain feeling I get when I’m the only person knowing what’s under my clothes.

Anyways, I got home yesterday morning, and while I was changing, my mother walked in and saw my back, she had an extreme reaction, a moment of absolute horror, and for me, I was embarrassed she saw that, but she also didn’t knock.

Now I am stuck not knowing how to proceed, because every single time I walk by her she looks like she’s got a multitude of questions running through her mind.

Has anyone had to explain something like this to their parents? Should I just leave it and allow time to pass and pretend as if nothing happened??