Nickel Skin Pigment My Girlfriend Has A Knot Under Her Skin By Her Temple About The Size Of A Nickel. It Hurts To Touch. ?

My girlfriend has a knot under her skin by her temple about the size of a nickel. It hurts to touch. ? - nickel skin pigment

exactly what can be? I thought it was an atheroma, has not increased but as a cyst is usually ...