Remedies for pulled muscle in lower back

I guess I'm slowly accepting that I'm no spring chicken any more. Friday I just went to work, didn't hit the gym or do any sort of lifting. Saturday morning we hit a nephew's birthday party, then on to my daughter's soccer game. The heaviest thing I carried was a few camping chairs and they were on a strap on my shoulder. Quick lunch at a Mexican place, then back home. Felt fine during all of that time. Don't recall bending over to pick anything up.

I sit down on the couch to watch a little football, and when I go to stand up about 45 minutes later, the lower back felt a little tight. Nothing too bad, just tight. It got worse over the evening, and when I got out of bed yesterday morning I felt like a 90 year old man. I stretched some, used my foam roller, and at different points in the day used either heat or cold on it. And some Aleve. Today I'm a little more functional, but sitting at this desk, if I shift the wrong way it kills me for a few seconds.

Any specific stretches I can do to loosen it up? It is at the base of my back, right above my butt. I can at least bend a little at the waist today. Yesterday was a cluster any time I tried to sit down, stand up, or lie down.