Lump on the back of head

I have a lump a little smaller than a quarter on the back of my head. It's hurts a little to touch but not much. It's a little soft but mostly hard.
I'm only 14 years old and I'm really afarid this could be cancer or a brain tumor.
When I tell my mom about it she tells me to shut up. And also I can't go to the doctor about it.
D:
PLEASE HELP ME.

[Michael Lim, MD]

Is the lump in the middle of your head?

[ShampooBottle]

No.
It's more at the very bottom. And there is one where that bone thing is to make it a bump.
One side of that is bigger than the other.
The one at the bottom is about the size of a penny and I cann't move it but I can like squish it down.
But not the other one.