If you turn off the car and let it alone for some period of time (15 minutes, an hour?) it will internally reboot all of the computers when you get into the car next time. I had a single frozen center screen happen once in my 2011 Volt as I was driving to a restaurant for dinner. The screen stayed on even after the car was turned off. After dinner it had fixed itself.
There is also a way to force an early hard reboot by going through some dance with starting the car and then opening the door for 15 seconds etc etc. and then getting out, closing the door and walking 20-30 feet away with the key fob for a certain number of minutes. You could try looking around this site for the instructions.
If you are not in a hurry, just ignore the car and do something else for a hour or two and then check to see if it has fixed itself.