Well I didn't pull a muscle but I did put my back out last week. I could feel it happen, that little twinge that means you turned just a bit wrong. Wow, the pain is awful, I understand how you feel.
Last time this happened to me I went to the chiropractor and he did some stretching and I bought a heating pad.
This time I am doing the bending and stretching and using a heating pad. (I never ice)
If you can, lay on the floor, legs bent and bring one up over to the opposite shoulder very gently. Do a gentle pull. Do the same with the opposite leg. If you have used a heating pad first you will be more flexible.
Also, check out the chairs you sit in. I ended up buying a new desk chair for home last week because my other one had always caused a twinge but I had figured oh well and didn't want to spend the money. Well, when the back is already sensitive using a crappy chair is definitely not a good idea.
I also changed out my chair at work for one with more support for my lower back.
As with all advice, YMMV, but this is what has worked for me.
It's been a week since I put my back out and I feel ever so much better. Good luck.