Woke up and noticed a pretty big bump on the top left of my forehead right before my hair. can't feel it unless i touch it and it doesn't really hurt.

This is c/w hematoma: a collection of water & blood which have leaked out of capillary blood vessels in the soft tissue between the skin surface & the bones of you skull which were damaged & leaked as a result of some injury, presumably which occurred while you were asleep or at least not remembered after awakening. Issues: nature of injury & did it possibly affect your brain beyond a minor concussion (not likely).