So I turned around and headed back. I had about two miles back to the Kingston Station. It wasn't all that bad. I babied the leg some when it first happened, and then the pedaling motion eventually worked most of the crampiness out. Doesn't feel bad at all now.
I still have some vestiges of my cold, but not too bad. The only complication is that my allergies started to kick in today. No let up for my respiratory system.