why my ipod touch camera are not working, its block sceen only.

That happened to mine once. I had to do a restart on it and then it was fine. Try pressing the Home button and On/off button at the same time and keep holding them till you see the Apple logo. Ignore the "swipe to shut down" prompt if it appears.

If not successful

Try the following:

- A reset. Nothing is lost

Reset iPod touch: Hold down the On/Off button and the Home button at the same time for at

least ten seconds, until the Apple logo appears.

- Restore from backup

- Restore to factory settings/new iPod.

If you still have the problem that indicates a hardware problem and an appointment at the Genius Bar of an Apple store is in order