Sometimes, things just ... happen.
I was in a hot yoga class (great in this cold climate) last night, partly to work/exercise my right hip. I think I've identified the source of my pain that I can feel only when I'm stretching my right leg; it's those (tight) hamstrings again. But this time, the pain comes from closer to the groin (so maybe it the upper segment of the muscles that got pulled). So, for now, I'm being extremely cautious in doing stretchy poses like the Triangle. In fact, I am avoiding Warrior 3, Half Moon and Vertical Split because these poses - basically standing on just one leg - place a lot of stress on the standing leg/hamstring muscles as well as my lower back ... my "core" alone is just not strong enough to support the rest of my body. However, that wasn't my problem last night (in fact, my hamstrings seemed to have loosen up a little in the hot room).
The problem was me getting out of a pose too quickly. I was doing the dancer's pose with a twist (literally!) and when I was done, I kinda collapse onto the mat and on my way down I think I turned something (neck?) too quickly and I could feel pain shooting up shoulder/neck region. Uh-oh. The pain kinda lingered for awhile before it took up residence in my right shoulder. So on top of my hamstring and neck (on the left where I had the pinched nerve), there is now also pain in my right upper shoulder.
I think I will/need to stay off the mat for a week ...