I have had the same symptoms this week as well. A "tinge" on top part of left chest and a numb feeling in my upper left arm. I have had this before about a year ago. Just had an EKG, chest X-ray from front and left side, "clean x-rays", normal BP and pulse. Having a stress test on Wednesday. I agree, I think it is a pinched nerve or something around the chest/arm pit area. Doc said, maybe shingles but I don't believe it.
Only a doctor can determine for sure what's happening. Not all arm pain or chest pain is heart related. It could easily be a pinched nerve or muscle pain that's radiating further. And pain will increase heart rate. To my knowledge (which is limited) I don't think a heart attack usually goes on for days.