how to access an iPhone 6s when you forgot pass code

I have an iPhone 6s, unlocked, 64GB, version 11.2. and I can’t access the phone because it’s asking for a passcode. It has worked find..I setup the fingerprint security and a backup passcode. However, it’s now asking for passcode after I restarted the phone and I never setup a numeric passcode……just the previous stated security and backup.

The is asking for passcode that was never setup….Help is greatly appreciated.