Thanks everyone. I really appreciate all of the comments and the advice. I realize that I made a HUGE mistake on Thursday by going to my Barre class, thinking that stretching and exercising would help (my general life motto is "Act!" -- I tend to think pushing forward is always the way.) Well, long story short: one of the exercises was a butt move called "the pretzel," which involved such twisting it definitely was not a good idea.
I have no tingling, numbness, or radiating pain of any kind. I've been able to really localize where the lower back soreness is (apart from exercise soreness). And I am taking the weekend off from any exercise and will continue on a regimen of Aleve, baths, and VERY gentle stretching. On Monday I'll see where things are and if there is still significant pain, I will see a doctor.
I really appreciate the help -- so good to have somewhere to turn.
xxxxx