The screen on your phone has gone out either by malfunctioning or damage and need to be replaced. If your phone still recognizes your touch (vibrates when you touch it, unless you had that setting turned off) then you won’t have to replace your touch screen digitizer only the LCD Screen itself. It depends on your phone but this can range from $15-$60.
If your phone is still under a year old and has no signs of damage then you might want to look into filing a warranty claim
. This will be your cheapest option and if this problem was due to a malfunction then its covered under the manufacturer’s warranty.
If there is damage then I recommend fixing it yourself, it is often cheaper than filing an insurance claim and is not as difficult as one might think to replace the screen.
But that’s what it is. Now you just have to choose what to do about it.
Good luck redraptor