Suggest Treatment For Painful Shoulder Blade After Injury

hi

i had a car accident 4 days ago and since then i have had sever pain in my back just near my right shoulder blade, yesterday i felt something move in my back so it now feels like something is out of place, and has made the pain alot worse, i cant really move my arm as its so painful, please can you advise what to do? and also what you think the injury could be, thanks