Try taking battery out for a full day and put it in the next day. Most likely the problem is that you overheated the phone. If that doesn't work, either get a new LCD screen or another phone.
The screen on your phone has a back light (invert er board).
Just like a computer, or a laptop screen once the back light breaks or becomes faulty no images can be seen on the screen.
Your best option is to contact phone manufacturer, and get the phone replaced with a new Phone.