If it's a pulled muscle
it will feel like a pulled muscle, i.e. sore, but a bit better when you exercise it.

If it's a herniated disc (when the squishy bit between your vertebrae gets damaged and pops out in a little balloon, trapping a nerve) you will feel constantly sore, and an excruciatingly bad sharp pain when you turn a particular way, which is often any way except one position in which you are semi comfortable.
( K2k6 has a proper job these days, Wed 22 Apr 2009, 8:46, Reply)