In reply to ClimberGirl:
I would have at least a week's rest, then follow a protocol of walking 5 mins after stretching to warm up, then run less than 10 mins, maybe 2 x 5 mins with a 2 min walk in between. Do this for 3 sessions (so a week for you) then add 2 mins to your run time each week until you feel you're over it.
If it persists it could be to do with your running style, your age and growing issues, or it might just be because you're under the weather and it would clear up anyway. Following the above protocol will set you up with the structural integrity to help avoid the same or other injury problems. Hard to have the discipline when you're 45 though, let alone 15! I can't stressenough how important it is to build up slowly with running to have some longevity and enjoy it without being constantly injured. I wish I'd followed that advice when I was 21!
A book called "Healthy Running Step by Step" is worth getting.