I don't see how it was the salesman's fault: you were driving and so you must take responsibility for your driving. And I don't see how the fact that the road and the car were unfamiliar has anything to do with it: you should have taken both factors into account when driving.

You should tell your insurance company that you have been involved in an accident that was your fault. This will affect your premium next year. An insurance contract is a contract of the utmost good faith and your insurance company is entitled to information about your driving record.

It is unlikely that you will suffer any further penalty, though. The dealership probably has insurance. However, since you were driving the car, it was your responsibility to check that you were adequately insured.

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JJ Rodger
2013 G350 Bluetec
1999 SL 500
1993 E300 diesel T
1990 190