I have recently had this problem, and i found a solution. You will want to buy a OTG cable, ($3 at walmart). Next, connect the cable to your Nexus. The last step is to also connect a mouse to the OTG cable (wireless works best). A courser should come up on the screen. The mouse enables you to access your Nexus as you would normally would.
"The digitizer (top layer of glass) and the display are a single item on the 2nd gen Nexus 7. If the digitizer layer is cracked, the touch screen will be partially or completely unresponsive.