What Causes Indentation On Forehead?

I no longer remember anymore when i got the sent in the center of my foreheadits already been a couple of years with it and it doesn t go away. I hate it cause its such an ugly sight. My forehead used to be perfectly round now it has that ugly dent! Today I noticed, not sure if just me, that it looks deeper maybe...but not sure. I m female 20 yes old now. I think the first time I started noticing it was when I was still 18. But since then it never went away. What causes dent in the forehead?? And can i make it go away naturally somehow? Without surgery cause I don t trust that method. I just want my forehead to look the way it used too again..