Most likely it is endometrial cells (so, traces of old blood that looks brown) left from your period being expelled. That's not dangerous at all. Just keep an eye on it, and if it persists constantly, you still really ought to check it out.
If possible, since you seem pretty worried. maybe you can talk to a school nurse or someone at a youth clinic? I know it might be embarrassing, but they're not allowed to tell your mom unless it actually IS something dangerous. And it might help to talk to someone about it.
My bad i do not have a cut inside i was letting my mind get to me im just really freaking out