help i think i messed up big time !!?

my friends and i were at an assembly yesterday and i accidentally told my friend that i broke my butt!!!! and she belived me!!! so now i need to find a way to actually break my butt so she won't think I'm a liar!! what, in your experience, are the best ways i can believably do this??? i already though of cannot balling off my porch so my butt breaks on the pavement but if i do that my mum will see me and i really don't want her to know about my deep lies!! what is a secretive, easy way i can break my butt without it hurting or anyone seeing? any help is appreciative