Hi,
This does not seem like a cardiac pain at all. It does not fit the profile of cardiac pain.
The other possible causes are:
Muscle pain: As you have surmised, it could very likely be nothng more than a pulled muscle. This is even more likely if the pain increases on movement, etc.
Acid reflux : this is also a likely cause. Such pains can be associated.
Costochondritis: If the pain is aggravated by touching or pressing, it could be due to costochondritis, an inflammation of the cartilage joint of the ribs.
Esophageal spasm: may be associated with difficulty in swallowing and heart burn. link
Psychological causes of chest pain are common and include panic attacks, anxiety, stress and mental duress
For you, acid reflux and muscle spasm are the two most likely cause. You should try initially with some antacid, like Mucaine gel (OTC) 2 tsf three times daily and Tab. Zantac 150 mg once daily assuming it to be acid reflux. At the same time, take Tab. Motrin 200 mg twice daily and gently rub Diclofenac gel (available OTC) on the area. If this does not help and pain continues more than 5 days, then you have to go for a medical check up. Link1 Link2
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