In order to recover your lost Nexus 7 password you will need basic computer skills and a piece of software called Android Tools.
Step 1: Get Android Tools
First step to recovering your Nexus 7 password is to download and install on your PC the Android Tools software. Once downloaded you can install the drivers manually.
Next, click on the newly created android tools icon on your desktop and click Run when the popup prompts you. Now you will get access to the Android Tools software to perform the second step.
Step 2: Recover Nexus 7 Password Actions
First you have to get your mobile device and press+hold following keys: Volume down and power (simultaneously) OR Volume up and Power (simultaneously) OR Volume up and Volume down and Power (all 3 simultaneously).
Although it will only take few seconds or a minute to take effect, you have to try these combinations until you get to the reboot menu. Be patient, you will probably not get it on your first try. Once you get to the reboot menu, simply connect your device to the PC via USB and choose next action.
Step 3: Consider Your Options
On this step you need to be careful and choose the action you actually want to perform. Basically, any option from 1 to 4 won’t result in any data loss while options 5 and 8 will erase everything on your device.
At first you probably want to try options 2 (Reset Face/PIN Lock) or 3 (Reset Face/Gesture Lock) or option 4 (Reset Gmail). Choose option 4 to replace your old Gmail account with a new one.