Did the back crack have any pain?
I personally don't think it's a muscle pull because you would feel that every time you used the muscles back there. When you strain a muscle you generally know it's strained because any time you get even remotely close to using it there's some pain involved. Kind of like perpetual painful soreness for a while.
Decompression is ok from my experience although not sure it would help much. I would get in there with some massage if possible to help keep everything loose.
Sounds like the form is a problem on the DL.. might want to work hip extensions a bit instead to help solidify the movement.