SusieQ says:

Costochondritis. It’s an inflammation of the cartilage and tissues that hold the ribs and sternum together. Hurts when you move and aches when you don’t. But, see your doctor for a proper diagnosis and treatment. Hope everything turns out okay.

bigbair7 says:

Could be in your tummy. Indigestion! Could be stress related. You probably need to have it checked. Pain is a generally a warning sign. Take about a half a teaspoon of baking soda in warm water. About one-half of a glass of water. Sit down and relax with slow deep breathing.
Bigbair 70—Never let them see you sweat!!!!!!!!!!!

zeb6219 says:

It could be a hernia, or an injury to the area on your sternal cartilage where your rib joins the sternum, or simple indigestion, or a big bolus of gas in your transcending large intestine.

mrcricke says:

Twisted ribs will cause much discomfort and can apply considerable torsion to the cartilage which attaches to the sternum. If you have any difficulty taking a full deep rapid breath without pain, can rule that one out. Would have need of doing a further work up to determine what is taking place.

Neither Republican nor Democrat says:

for years I had pain attacks that were right where you say. It felt like a heart attack, but they finally figured out it was gall bladder stones passing. They took out the gall bladder and now I’m good as new!
You should get to a doctor and not take chances.