Hamstring Worry

It's Monday afternoon and my hamstring is still quite sore. Yesterday, I found that for the third run in a row, I could feel severe tightness in my right glute and hamstring for most of the run. I'm hoping this isn't shaping up to be an injury.
Friday's run turned out to be a steady 10K, perhaps tempo, but the freshly falling snow slowed me down a bit. Still, once I managed to get myself out of bed - harder because there were no run buddies to meet - I did enjoy being out in the snow. I ran past Dow's Lake and all the way to the Ritz cafe at Fifth Ave. and the canal before I turned back. I did see a few other runners out at that hour leaving their shoe prints in the snow. It wasn't cold at all, but a bit wet. My time was just over 58 minutes.
Sundays run was not as successful. I was attempting a 16K but I ran with the group doing 29 with a plan to turn back at Laurier, after a Hog's Back loop. I'm not sure it amounted to a complete 16K. In fact, according to Dwayne's Garmin, it might have even been shy of 15K. It wasn't a great run. The company was fine, as always, but I felt like I was fighting another cold, or perhaps the same one I've been fighting all fall, my hamstring was very tight, and I really had to pee badly. One more trip to the bathroom before we set out would have made all the difference. Sometimes that feeling disappears on the run, but not yesterday.
Yesterday's less than stellar performance doesn't really matter. I'm going to nurse my hamstring a bit and hope for better runs this week. If anyone has any tips about how to stretch it really well, please let me know.