Thanks for posting your query.
You might having soft tissue injury
rib over your left side of chest .
In deeper bruises you will not be able to see these bruises, they can still swell and cause pain.
I suggest you to consult an orthopaedician nearby for a detailed examination. You may get the X-ray of the area affected under his/her guidance to rule out any fracture
In the interim,ice fomatation to the affected area, take anti-inflammatory drug like motrin
to reduce pain and inflammation. Rest well.
Dr Saurabh Gupta