The answer depends on what state you are in. In NY, you would be able to sue the bar owner and the person who assaulted you, provided that the bar owner knew or should have known of the person's propensity to stab people. I suggest you contact a PA lawyer to know all of your rights.
If you were stabbed inside a bar, you may be able to recover from the person who stabbed you. It will depend on whether you started the fight and that person was acting in self defense, or if that person acted negligently or intentionally in stabbing you.
You may also be able to recover from the owner of the bar, if the bar knew or should have known that the person with the knife had the knife and was likely to injury other patrons, or if there was a history of such fights in the bar and they failed to provide adequate security for the customers of the bar.
You should consult with an attorney about your rights.
