Which procedure would help minimize the v shaped protrusion on my forehead? What can this be? (photos)

I've always felt like I have had a little 'forehead dent', as I called it. But over time it's gotten worse, and the 2 protrusions make a V like shape right about my eyebrows, which creates the forehead concavity. I have gotten Botox in my forehead many times, I was trying to look back at pictures to see if it was helping or making it worse but I couldn't tell. I was wondering if this was a muscle bone or my skull. Is this frontal bossing? Would filler be an option or something else?