Does it hurt on one side in particular? It is very possible that you have either gas or are constipated. Sometimes gas can be VERY painful.
You said you had just done a lower body work out. Do you stretch first? Did you vary this from previous workouts? I had lower abdominal pain for several months some years ago - all possible abdominal problems were ruled out. I finally saw a doctor who related my abdominal pain to a problem I was having with my lower back. The abdominal pain was 'referred pain' from my back problem.

If it goes away - it was probably nothing. If it continues into tomorrow - or if you have a temperature elevation and the pain is on the lower right side- I would see a doctor. Do you still have your appendix?

Hope you feel better!