Hi, I'm Not Too Concerned With This, But I Am

Hi, I'm not too concerned with this, but I am still curious about it. Usually, in the morning I will have a red line on the left side of my forehead. It is approx. 1-2 inches above the right side of my left eye and goes to the left and up, 2-3 inches. It isn't very thick (A few mm) and I think it might just be a vein showing through my forehead? I have no idea when it began, and I can only recall it being visible just after waking. Thanks for you time.