being sued

I recently sold my car to an individual and had them sign a contract as they were paying monthly payments to me. I sold my car back in November of 2015. But the person who purchased the car didn't put the registration under their name they kept it under mine😒. They got into an accident in May 2016 and damaged someone else's car. He paid me their last payment in June. I had no idea they had gotten into an accident at all. Now I'm I'm being sued by the person he hit and have to attend court because he didn't put the registration under his name until October 2016. I am 32 weeks pregnant and have to attend court for something I was not involved or present in... it's so stressful to me as my baby will only be only 2 months old.. idk what to do I have never been sued for something I didn't do before any advice ??