I'm glad you hav an appt in the morning. Shoulder injurys can be complecated. Was the accident your fault? Does the driver have insurance, if his fault? I had what seemed to be a simple shoulder injury, it got complicated fast. To make a very long story short, after 6 months of conservative therapy, I ended up having a shoulder acromioplasty, and was off work for a total of a year. It was not fun, as I couldn't work. I would restrict movement until you see your dr in am. Is it an ortho? They are better qualified to treat this. You will probably need a MR or X-rays at least.
I hope this helps. Rest!!!
Hugs & Prayers, MaggieI
One more thing...I think it's muscular. If I have someone raise my arm, it doesn't hurt, but if I use my muscles it hurts.