Is it a popped rib, or effect of the flu?

I'm a teen, and I ended up getting a flu-like sickness about 2 weeks ago that lasted for 4-6 days. I vomited only once near the end, and most of it was just chills, lack of strength, stomach pains, and such. I couldn't even walk straight. I went back to school for a whole week without any other symptoms and most of my strength is back now, but this morning while walking to my first class I bent over to cough and it feels almost like I pulled something around the bottom of my left rib. Two classes later, I told my athletics coach if she wanted me to run the work-out even though it hurt to walk, and she told me it was popped rib? I'd like to know the likely-hood that it is a popped rib or not. I can still walk and it doesn't hurt so much anymore now that I've moved around a bit now and such, but it hurt really really bad just to breathe. Any thoughts would be appreciated~