Greetings, sorry about the pain.
You seem to have muscle spasm at rib cage area. Your are starting to develop hump back, not to be worried. Solutions is around.
Next Steps
get to see a physio specialised is posture correct. this will help cure your pain. on meantime lie on hard surface for couple of minutes flat will ease spasm plus icing will help.
Health Tips
if unable to solve, then you can visit me to get sorted