On Tuesday I had a steroid injection into my left side (around the L5 level). The injection was administered above my left butt cheek. Today (Thursday) I have woken up with a bad headache. It feels like I have a bad hangover, even though I have not had alcohol in a long time. The other weird thing is, it is strictly on the left side of my head. Could this be related to my injection? And, if so, is this normal?