Why do I suddenly need to enter a password to open my Nexus 5?

[AC Question]

For no reason, when I try to unlock my phone, they ask me to enter a password. I never used a password before. Now the only thing I can do is emergency call...

 

[Golfdriver97]

Welcome to the forums. I don't think I have heard of this before. You can try taking the device into your carrier store. They may be able to help you bypass the password/pin.