Not to worry! Your credit score and linked bank accounts are still linked to your NerdWallet account. What you're likely looking at is a new NerdWallet account that was created when you selected "Continue with Apple."
If you choose to hide your email during the process of selecting Apple ID (by using the anonymized email option), then a new NerdWallet account will be created instead of you gaining access to your existing account. This new account will not show any of the information from your existing account, like your credit score or linked bank accounts. Nothing happens to your existing account in this situation - it’s still there.
You can view your original account by logging out of the newly created account, then signing back in using your original sign-in method (either your email and password or Google authentication).