I used to have terrible lower back pain and my dad told me to stretch and work on my core strength. I was actually shocked how quickly it got better. One of my teammates started to get bad back pain a few months later; she went to a physiotherapist and he gave her a stretching/core routine to do at home.
The best long-term treatment is to stay strong and fit, maintain a healthy weight, and focus on correct posture to avoid creating further problems.
In the meantime, you can always take medication or try a heating or cooling pack (or alternate between the two).
If it continues or gets worse be sure to see a professional.