new 4th generation iPod touch doesn't have the app store
I assume you have all your media synced to iTunes on a Mac or PC? Then it's save to do a full restore of your iPod touch.


  
  Disconnect the USB cable from the iPhone, iPad, or iPod touch, but leave the other end of the cable connected to your computer's USB
  port.
  Turn off the device: Press and hold the Sleep/Wake button for a few seconds until the red slider appears, then slide the slider. Wait for
  the device to turn off.  * If you cannot turn off the device using the
  slider, press and hold the Sleep/Wake and Home buttons at the same
  time. When the device turns off, release the Sleep/Wake and Home
  buttons.
  While pressing and holding the Home button, reconnect the USB cable to the device. The device should turn on.
  Continue holding the Home button until you see the "Connect to iTunes" screen.
  If necessary, open iTunes. You should see a "recovery mode" alert.
  Use iTunes to restore the device.
  


also see: official documentation