It sounds like you could have pinched your sciatic nerve. It's really easy to do when you turn from the waist, and right from the low back and down the left leg is where the sciatic nerve runs (and for some reason, it must have to do with most people being right handed, it's almost always the leg leg.)

You can see a chiropractor to make some adjustments to your back so that you don't do yourself an injury again as easily. Put cold packs on your lower back to reduce swelling for 15 minutes at a time, ever one or two hours. A cool soak of your leg muscles wouldn't be a bad idea either. Even if you can't see the swelling, it may just be there and the coolness will help reduce the swelling to prepare it to be re-adjusted before you visit the chiropractor.

The reason why your leg is sore is because, even if you didn't notice it, you were walking a little differently to keep the pain at bay. It may be the nerve still, but I bet more on the muscles cramping up as a result of trying to defend the nerve from pain. Take some calcium/magnesium which will help your muscles relax. Potassium can help quite a bit too.

I hope you feel better.