Suggest Treatment For The Painful Pimple On The Head

I have a painful pimple like thing on the back of my head but it wouldn't pop. My mom says its a mole but I thought it was a pimple or ingrown hair but it wont pop at all. Why all of a sudden would it raise like that over night and hurt like a pimple? will it go back down an be flat with my head? if it is a mole why would it raise because its irratated maybe i caught it with a brush an will it go back down?