Pain in left side chest when bending over?

Likely Muscular: Pain with motion is likely musculoskeletal. If it doesn't resolve or you have other symptoms see your doctor. All the best.

See your physician: Pain in the chest on bending over may be due to some strained muscle in the chest wall. But there are so many different causes that a physician would want to ask you specific questions, and then examen you, before making a diagnosis. As always don't try to diagnose yourself on the internet. If you are experiencing a new or unusual pain seek medical advice.