It could be Costochronditis.  Check with your doctor.

http://www.diagnose-me.com/cond/C598186.html

It could also be a fractured or bruised rib. In both cases just time, rest and pain medication like Ibuprofen are the only cures.

It could also be pleurisy which is inflammation of the lining surrounding the lungs.  A chest xray will diagnose that.

It could also be a Vitamin D deficiency. A simply blood test will diagnose that.  Part of what kept me off work on disability was severe pain in my ribs and eventually my entire skeletal system from head to toe. I thought I had bone cancer it was so bad. I was referred to a pain clinic. A blood test showed that I had virtually no Vitamin D in my body. I was put on prescription high does for 6 months and then a maintenance dose daily for the rest of my life.  My pain was almost gone by the end of 6 months, and at the end of a year it was gone completely.  See your doctor and ask for a blood test.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi