Bone Bruise In Acromioclavicular Joint

Hello, About 3 months ago I had quite some pain in my left shoulder after weight training my chest/shoulders, the pain gradually spread from my shoulder up into my lower neck and although i still had full movement it was v painful and i certainly could not lift any weights..

The doc sent me for a MRI scan which showed i had a bone bruise in my AC joint, i then got a course of massage and ultrasound treatment... after about a month of doing nothing i returned to the gym for some light training but no direct shoulder exercises and very light on the chest, 30kg etc..

3 months on and not having trained my shoulders directly or gone very heavy on my chest i still have an annoying ache in my shoulder going up into my neck that comes and goes.. It typically comes when I'm sitting, as soon as i start moving again it goes away.

I can also see that the AC joint in my injured shoulder is slightly larger/protruding more than the one in my good shoulder... Should I really be laying off all upper body exercises till its fully healed? from what I've read on bone bruises this could be up to 6 months?? not so appealing but then neither is training the way I am now and still having pain...

Also I don't really understand how an injury like this would happen, is the bursa not meant to prevent the humerous and AC joint from coming into contact? also the MRI showed that I did not have inpingement syndrome.

Would really appreciate any advice on this.