Reset device in Recovery mode Nexus 5

See options for backing up and restoring your data before performing a factory data reset. To perform a factory data reset, select your device from the list below and follow the instructions. 

1. If your phone is on, turn it off.
2. Press and hold the Volume Down and Volume Up buttons, and then press and hold the Power button at the same time until the phone turns on. You'll see the word "Start" with an arrow around it.
3. Press the Volume Down button twice to highlight "Recovery mode."
4. Press the Power button to start Recovery mode. You'll see an image of an Android robot with a red exclamation mark and the words "No command."
5. While holding the Power button, tap the Volume Up button once.
6. Use the volume buttons to scroll to "wipe data/factory reset" and press the Power button to select it.
7. Scroll down to "Yes - erase all user data" and press the Power button to select it.

Note: If your phone becomes unresponsive at any point during these steps, you can restart it by holding down thePower button for several seconds.