What if a bar patron aggressively grabbed and head ed an 18 yr old line cook while the cook is working?

My friend and I were looking at a co-workers car that he just bought and on our way back inside the restraunt from our smoke break, a well respected friendly faced patron came outside and started joking around with us about racing our cars vs his. I have a 1993 ford taurus and said it would win vs his relatively new F150 and then the patron giggled and asked about if he used his super charged jaguar which my friend teasingly called a cat car in which he responded with joyful laughter. He said we didnt stand a chance as we were starting to go inside again and get back to work. We responded by saying only time will tell. The patron giggled and went back to the bar and my friend and i went back into the kitchen and started working again. About 20 minutes later we see the patron walking toward the kitchen door thinking he was coming to continue the joking around about the cars. He came right up to me and my friend and grabbed the back of our necks and followed up with a head to both of us. My eyebrough was cut and my friend suffered a headache. The was no retaliation or harm received by the patron. There were multiple witnesses and i want to sue.