The same thing happened on my aunt iPhone after she dropped down the stairs and I got it to work. Her problem was that she had a black screen but everything seems to working because you can still hear everything. And I think that the same problem you having.!My soultion is press the power and home screen down to turn it off. Remember how you usually turn it off on regular iPhone to you also have to slide it so that it's completely off. Then turn it back on and the apple logo should appear again and then wait for a minute and hopefully you can be able to see your lock screen when you come back too it