Can you get a refund on privately sold cars?

Hi, I sold my car about a month ago in qld i had a guy ring me up from nsw saying that he was flying up in the next couple of days to purchase the car. I told him i wouldnt be able to get a rwc in time he was fine with that, i left the rego on the car because it had a month left and he needed to drive it back to nsw. He has know rang me up saying he has had all these problems with the car getting it mechanically sound and cant be registered in nsw because was written off previously (which i knew nothing about it). Hes know trying to take it to the courts and wants a refund because i with held information about the car. Do i have any legal obligation to take the car back or pay for the repairs??