What Causes Indentation On Forehead?

Hi so lately I noticed a indent on my forehead. When I press my finger againist it I feel the indent.. When I laugh or get mad the indent starts to push out . Thinking it's a nerve that pops out .. Whenever I put a SnapBack on I get a Sharp pain right above my right eye.. This indent goes straight down my forehead and stops right beside the start of my right eyebrow.. Sorry if I couldn't expalin this properly