Hello and thank you for using HCM.
I carefully read you question and I understand your concern. I will tray to explain you some characteristics of a typical heart pain and help you understand something.
In general cases a heart attach, a typical heart pain presents as a central
chest pain like tightness or heaviness, squeezing pain. It might irradiate to one or both arms, neck or jaws. It continues 5 to 10 minutes. In a
heart attack it last more than 20 minutes, it is a very heard pain and it is associated most time with sweetness,
nausea, dyspnoea or breathing difficulties and palpitations.
So, if you feel that you are having pain in your arm that last all day long i would say that this is not related to the heart, because something should has happened during this time if it was a heart attack.
If this pain reassembles what i explained before, if it exacerbate during an exertion than you should consult a doctor.
You didn't mention you age but in my opinion, if you do a simple electrocardiogram to the ER in the moment that you have pain would help us to understand different thinks and of course you would feel much safe.
Hope I was helpful. Wish you good health.
Best Regards