What Causes Raised Moles/freckles?

Hi, I have just noticed one of my moles/freckles on my side seems to have elevated slightly, it was always raised slightly anyway but it just seems to be a bit 'taller' when I have noticed today. It is perfectly round, its pink but does have a very tiny black dot in it, also feels rather 'hard' across the top, and can be painfull if its rubbed against something as it 'folds over' slightly...