Auto Pedigree never disclosed accident damaged car

In November 2013 I purchased a vehicle from Auto Pedigree Kempton Park, the sales man told me the car was never in an accident and was given to them from a rental car agency because that agency gets rid of it when it reaches certain mileage, the problem now is that I'm trying to sell my car and when the car was inspected by the new buyer he discovered that the car has been in an accident and he can only buy it at a very low price because of that. I want to sell the car now and I'm stuck with it, please help.