Connect to iTunes and sync, if the display still doesn't show anything, restore. If it still doesn't show after that... It's most likely hardware.
If it's within a year of purchase, or 2 years if you bought Apple Care, then I would tell you to make an appointment with Apple.
If it's not under warranty, then it might cost you to get the repair done. If that is the case, shop around and I am sure that you will get a deal.