Has a chest xray been done to rule out any rib fracture, chest infection, or air in the pleural space?
There could be several causes of the symptoms you are having including a muscle pull, injury or trauma at the site, chest infection, gall stones, etc.
Do you have any associated symptoms?
You should apply some local pain relief medications, take some oral pain relief medications, maintain a proper posture throughout the day, try some warm compresses.
You could take some antireflux antinausea medications and see if they help with your symptoms - this could be pain due to reflux or GERD.
Consult your doctor if the symptoms persist and discuss whether you need to get any investigations including a chest xray and ECG done.
Let us know about how you are doing and if you need any other information.
Did you find out what it was?