You may have irritation that causes swelling. I could try anti infammatories like ibruprophin or motrin and try and decrease activity in that arm for a while. It also could be nerve pain but you should rule out the simpler possibilities first.
Welcome to the Forum.
It sounds like it could be a pinched nerve but more than that, it sounds like it's related to your cervical spine. Many times when you have problems in the cervical area, you will experience pain and numbness that radiate down one arm. Rarely both arms but I have heard of it.
Like the first comment, you might think about an MRI and possibly with contrast.
Make an appt. to see an Orthopedist. They are the best qualified to diagnose you.
Yes, that's definitely one possibility. You probably need an MRI on your shoulder. You should see a dr and let the doc diagnose it.