Maybe you strained something....chest pains CAN mimic other things besides heart trouble, or COPD...which is kinda severe, and I think, uncommon in younger people. Maybe Juni pulled too hard on your leash? Or, you strained something while moving??? While it might be serious...I think without any other symptoms, it is probably muscular in nature..

I AM NOT A MD, I DON'T PLAY ONE ON TV, AND THIS INFORMATION IS MEANT TO BE ONLY EDUCATIONAL. YOU SHOULD ALWAYS HAVE YOUR SYMPTOMS EVALUATED BY A DOCTOR.