You can't just turn off the PIN. Either you may have entered it incorrectly or, if you have more than one account, you may be logging into the wrong account.
Another option is to select a different login verification such as password, face recognition (if you have that) or anything else you originally set up.
In any case, the worst I know of (and I'm only a hack, not an expert) is that you will have to reinstall the Windows OS. During that you will be asked to create a new account which will ask for a PIN. Once you do, it eventually will ask if you want to restore from a previous backup which may simply solve your problem.
If you're on a home system without visitors accessing it, you may want to get rid of the PIN which will require the above direction to either change the account type or create a new user without a PIN.