Try mixing your vitamin I with chocolate and maybe read some of The Oatmeal
While chocolate and comics help, I'd also suggest some gentle stretching of the hip flexors. Often if I've done a lot of sitting, my hip flexors get tight and then my lower back feels tweaky when I run. But if it hurts-hurts, you should go see a doctor.
OK, I have scheduled a massage for tomorrow morning at 9:00. I have thought a lot about retirement. Maybe I'll go home and lie down.