Brief Answer:
Most likely a pulled muscle.

Detailed Answer:
Hi,
Thank you for using Healthcare Magic. From the description you give of your pain, it is most unlikely this is due to a heart problem. It is more likely to be a pulled muscle. You may not have noticed at the time but it is easy to inadvertently strain a chest muscle without noticing and then suffer afterwards.
My advice is to take paracetamol and ibuprofen for the pain. Apply a warm compress to the area regularly. Try to rest from physical activity for a couple of days. The pain is likely to subside during this time.
If you are still in pain after 2 days then my advice would be to see your doctor for an examination and perhaps investigation to exclude a heart problem or possibly a chest infection.
I hope this is of help. If you have any further questions, please do not hesitate to contact me.
Regards,
Dr K A Pottinger

---