Please I Need Your Advice, My MD Slapped Me,

My MD Has Done The Worst, Please I Need Your Advise.

My name is Sewa, I work in an hotel at Iyana Ipaja as a bar supervisor. Am a graduate of Lapostech (HND). I work 24 hours because of the nature of my job and its a day off and on, meanwhile mine has been 3 days on and one day off because I make more money than others. Before I got to this hotel as a staff, they make lesser than I make now. Per day, my target is 100k but I make 130k at worst because we have club in the hotel as well.
It happened on friday when a customer wanted to buy a wine and I was eating before the customer came in, I was still chewing my meat when the customer came in and I tried to attend to the customer with the meet in my mouth because I do not want to delay him. In that process, my Managing Director came in and slapped me 2times in the presence of customers and even guys that were making wooing me, his reason was that I attended to a customer while eating. We not have break time in this my place of work o.
He slapped me and I worked away to continue my work but I want to revenge. I do not want my silence to be in vain.
My manager has been begging me not to resign because I dropped my resignation letter that day. He is begging me to come back.
What would you do if you were in my shoes?