I know it is simple, but have you tried rebooting it? Should that not help then it sounds like either the display is going/gone, or the connections to the display have come loose. The only want to know for sure is to open it up and check.
That said, if your device is still under warranty, you should not open it up yourself. If that is the case, you need to contact the manufacturer about having it repaired/replaced.
However, if it is no longer under warranty, then you can do the work yourself (if you feel comfortable doing so) or take it to a local tech/repair shop to have them do the work. If you choose to try and do the work yourself, I am sure you will be able to find instructional videos online that can walk you through the process.