My LGK7 phone screen is messed up shows different colors

I had been dropped my phone, the screen was cracked but it still worked, the screen was fine nothing was wrong. But then the day I took it to school, and when I checked it so I could see what time it was, all of the sudden the screen started to act up...I honestly though it was nothing, but when I turned it off and turned it back on, the screen was in different colors and there was black spots on the top left corner of the phone. I honestly don't know what happened to it, I tried to see if it would go away, but nothing works