"Growing Pain" in length of my arm...don't know why; please help

I didn't know what other category to put this under; this seemed the closest.
I got it the morning after I did some cardio, which included some light weight work on the arms. I only mention that b/c I can't see any other reason this would happen.
The pain goes from my shoulder to my wrist; I've noticed it that morning, the next night, then the next morning. The top of my shoulder, where it meets the arm pit, is a little sore; I can tell by touching it, but it's barely noticeable. Would this, in turn, cause this other pain? It feels like a growing pain and hurts more when I use my arm but it also hurts just laying it by my side. I take advil for it.
Has anyone experienced this and/or know what this is? Will it go away?

Thanks

Oh, no. I am trying what you said actually. And no, nothing is broken.

No, it doesn't. I swear I always get the weird stuff.
It just happens w/nothing that I can see to trigger it.
I have the same feeling somewhat in my other shoulder now too.