When I do the AP part of orientation, this is probably by far the most commonly asked question of me. I usually start off by telling them that you should have left the area long before this happens and found an LOD or AP. Would you get fired? depends. Our HR and AP ETL's both say if its in self defense it would generally be ok. If they swing at you and you hit or push back just to get distance so you can get help, is way different then did they swing and you lay them out and pummel their heads in with a nearby metal weights from sporting goods.
Everyone wants to be the tough guy, but in most self defense you goal is to just get out of the situation with minimal or no injury, if that means turn and walk away, or turn and run away, then you should do that. If you have to push them so you can run, do that. This isn't a movie, or a sporting event, if your really at risk of getting "beaten up" or injured then you have to take advantage or vulnerable areas. A police officer isn't going to show up and say oh you hit them in the groin, and throw a flag on the play.
Just going to add, If you do want to stay and fight and duke it out, its hard to say it was self defense when you have a way out, and yes you might get fired. It might look like your a punk, but you will be the punk without a black eye and a job.