The dealer has to have given you a temporary registration for the car.
You can drive it up to the date that that expires.
If they didn't give you a temporary registration, then you can drive it up until the point that a Police Officer pulls you over, and asks you for your documents. At this point, you will be given a free ride to jail, and your brand new car will wind up being towed to the nearest Police Impound lot, at your expense.
If you didn't get temporary registration papers from your dealer, I HIGHLY RECOMMEND that you contact the dealer IMMEDIATELY to get this issue resolved. And don't drive the car until you do.