What Causes Swelling In The Shoulder Blade Post An Accident?

I was in an accident three months ago and as a result had a dislocated left shoulder. It was fixed that same day. I am back at work, and doing therapy, but now, my left shoulder blade keeps swelling up and i'm beginning to feel a strain on my neck. at times it feels like there's something interferring with my breathing also. what do you think causes that..