It could be quite a few things ranging from serious to not so serious. Has it just been recent or have you had previous episodes? Sometimes stress will give you this kind of feeling. You also might have put your back out. It's hard to tell.

I actually spent this afternoon in the emergency department with chest pain. But it was different and because i have a health condition that makes my heart race. I had all these tests... seems everything is ok... just need to take more heart tablets.

If it persists for more than a few more days I'd see your doctor... or at least give Nurse-on-Call a ring. They are usually very helpful. Let us know how you go.