If the person who actually committed the offence was arrested then they will have been finger printed, if you can prove that your finger prints are different (which I'm sure you can) then you have proved your innocence, unfortunately if the driver was not arrested and finger printed you could be in the shit, either way you ought to speak to the police as soon as possible, I'm sure that once you have explained everything to them they will try to help. Good luck mate and let us know how it works out.