My wife is a massage therapist. When I get a sore back the first thing she suggests is the "ice and rice" treatment. It has cured me more times than I can count.
Ice & Rice treatment consists of alternating an icepack for 10 minutes, nothing for ten minutes, heatpack for ten minutes, nothing for ten minutes, repeat...
I use a soft/flexible blue ice pack wrapped in a towel for the ice part. The rice part of the treatment is pretty cool. It is a DIY microwave heatpack:
Take a clean tube sock, fill it 3/4 full with uncooked white rice, then tie a knot in the open end of the sock to keep the rice in.
The heating time for the rice sock depends on the size of your sock and the power of your microwave oven. Experiment to find the heat level you are comfortable with. Mine is 2 minutes 30 seconds, but my wife likes it at 3 minutes even.
Hope this helps.
If it doesn't you might try a combination of massage and chiropractics. The two combined are very good for pain relief.