Your screen is dead. You can try contacting customer care to see if your handset is still under waranty and, if it is, they will replace it for you as long as there is no water or other physical damage.
If your handset is no longer under waranty you can replace your screen yourself. It is relatively simple to do and you can find the replacement part for between $20 and $40 from numerous sources online (ebay etc.) I recommend repairsuniverse.com as they use all OEM parts.