I agree that you should tell your parent(s). Chances are it is just a boil that is coming up that was caused by your panties rubbing. Nothing to be scared about.
Honey you need to tell your Mom right away, it's not your fault, it's nothing you have done. But it needs to be check right away...go tell your Mom, right now...It's OK, don't be scared....If you don't get it check, that's would be scary. Now go tell your Mom....Please