do i have a case

I am not sure whether you could claim that he assaulted you as I amnot sure based on the limited facts as to whether he meant to hurt you.  It sounds like an accident on his part/being rude.  You may be able make out a negligence claim against him as he failed to hold the door for you once he took on the task to do so, but, i am not sur if that is what happened.  What you do have however, is a workers compensation claim.  This will get your med bills paid for and you can get money possible future surgeries or other medical requirement you will have.  I suggst filing a claim with the human resources dept.  The i suggest getting a lawyer to represent you in your claim.  Workers comp lawyers ususally get paid only if you do.  Plus, the idea here is for you not to have to pay for the medical expenses.  I am not ruling ou the possibility of a claim against your boss, but I would need to know more facts about the situation and how it happened that the door hit you.