Is the pain sharp or dull? Does it feel like pressure behind there? Does certain movements, like squinting increase the pain? Because I had a dull ache behind my left eye. The pain would increase with certain movements with my eyes. I don't really know what it was but I assume it was just an headache because the pain would radiate above to my head. It could be pressure. But I am no doctor of course. If it concerns you, and has been there for 4 days, then perhaps go seek professional advice and go from there. But as of now, since you can't really do anything about it, you should perhaps let the worry go.