Martina when you lift your arms out to the front, like driving a car, computer work, it lifts the ribs against the outlet under the collar bone area to compress the outlet.
If your nerve dermatones are acting up and this painful, I would contact the doc, even your PCP for a shot or Toradol. It is none narcotic anitinflamatory that helps in about 15 minutes.
The other thing is the pack of steroids...what the heck is it called, metropropal?

I don't remember if you said your are working, keying. If this is the case and in are in this large of a flare up, you may need to rest the arms for two weeks at least. With the treatment of the toradol etc.

If this repetitive from work, start a w/c claim now so you can get the paid few weeks off and medical needs covered. Including going back to work with modifications the OT would request. I think you had some, but sounds like you need more.

Are you on the phone a lot lately? This may e inciting that arm.