Nevada has a very short time frame within which to back out, cool off, rescind with no penalty. 5 days with day one being the day after you sign the contract. If you are within that time since you bought, you're golden. Beyond that, it is very difficult and can have significant affects on your credit.
Very important: When did you sign??
There will be instructions in your contract- probably not obvious- likely near the end, perhaps on the signature page for the procedure and address to write to cancel the purchase.
Even if you are a day or two late, get a letter in the mail, Certified, that makes it clear that you wish to cancel this purchase. No need to provide a reason. It's your right.
Jim