I am having pain under my left shoulder blade, and in the lower part of my left arm, should I be concerned my email is (removed per site rules).

I am having pain under my left shoulder blade, and in the lower part of my left arm, should I be concerned with this, I am 42 years old

Anyone age 42 needs to have a regular doctor or clinic with NPs and PAs and nurses.

Two suggestions, JUST suggestions:
The broad range of muscular and nerve irritations, often from using a computer too much in the wrong ways, or carrying a heavy bag on that shoulder, or sleeping on that side too much, or carrying a baby.
Heart conditions, which can often have symptoms in the left arm.

I am 68 and have lots of problems in my right arm from computer use. Let us know if you think that this could be a possibility (IF you are left handed) and we can advise. Even if you are right handed and sit at a desk all day, you can lean one way too much.

As for your heart, PLEASE see a doctor right away if you think there is no chance of minor muscle problems, or if you haven't had a checkup in a while!

Best get FACTS before your FEELINGS get you carried away. Have this checked by a physician and save yourself unnecessary worry and stress because it could be a symptom of ANYTHING.