I've heard the stretch/no stretch theories, but stretching works well for me. I would think that a lot of it has to do with individual physiology. And if you've never stretched how do you know that it won't improve your running form? But I know many runners, many who are fast, who do not stretch at all. A lot of stretching for me is about range of motion and joint mobility, and I've heard that stretching helps reduce lactic acid build-up after workouts... which means faster recovery, and improved following workouts. But, porw0004, if you haven't stretched, it might not hurt to give it a shot to see if that helps the back pain, and if there are no results then stop stretching. Also, just curious, is the pain a soreness or a stinging/sharp pain?
Like it was mentioned, warming-up is equally as important if not more.