“Forehead Indentations?”

I've stopped sporting bangs and notice bilateral indentations above my brow. They appear when light is directly overhead, and at certain side angles are more prevalent. I cannot discern if these are caused by a tight corrugator muscle, sinus issues, a tight frontalis muscle, an oddly shaped skull, or something else. I would like to determine the cause and have an appropriate solution, be it massage, Botox, etc.