Screen Turned WHITE color after I 8.4 updated my iPhone 5

Hey everyone,

I updated my iPhone 5 to iOS 8.4 just an hour ago. When it restarted my screen turned White, uni-color. just white.

What am I supposed to do?

Oh! Of course it's protected by a screen lock. The assistive Touch is activated and can be seen despite of the white screen, and of course I can't switch the device off as its screen is locked.

Help, please!