How am I supposed to deal with this lawsuit?

So, the event that triggered the suit happened about a week ago, and when it happened I was actually on a class trip in Chicago, we were on Michigan Avenue at the time to check out the Magnificent Mile. I was walking with a few friends and we went a block or so off Michigan to find some place for lunch. On the way to the restaurant, this really shady looking guy started following us. We started walking a little faster, and that's when the guy put a knife to my back (since I was towards the back of our group), and demanded we give him our valuables. Since I'm a black belt and have had a lot of experience in knife defense I fought back and got the weapon away from him (I kicked it out into the street). Luckily there was a cop nearby who arrested the guy and the rest of the day passed without incident. Now, a week after the events occurred, I found out on Friday that this mugger has tried to sue me for assault and battery for some reason. I can't go to court up there because of school, but I was informed that I would have to pay out a large chunk of cash if the court ruled in the mugger's favor. How should I deal with this? Should I get a lawyer? Or should I just wait and see what happens?