What Causes Stinging Pain In Ribs?

hi, for the past three months or so I have had stinging in my left rib when I run. Its so painful that I have to stop jogging. This is very demotivating, as I love to run.
While when I do other kinds of activities like biking, swimming and kickboxing there are no problems.
What can I do about this?? I know its not normal pain in the side..
thanks