sorry bout the necro but this is what's happening to me ALL THE TIME when I'm meditating with my eyes open or trying to use my intuition.
Q&A: Pressure in forehead — Sri Chinmoy
That said it was because I'm meditating in the wrong place. But if its due to my third eye opening... I'm kind of scared aren't there like demons and stuff in the astral realm, my life has enough problems as it is...