I have a knot in my left fore arm and the whole arm hurts and so does my heart what is it?

Difficult to tell: Moles are different than a knot. If you have a knot in forearm it could be simple swelling due to injury or a bump or can be serious such as tumor and you have some heart related issues as well u can have radiating left arm pain if you are having a heart attack so it is not possible to diagnose the problem without all the details so please contact your family doctor as soon as possible.

Not quite: Enough info. Generally takes a much more detailed history.