Why is my screen only bright at the top and the rest is dim?

Hi,

Pretty sure this happened because I dropped it...I have a 2016 Galaxy S7 and for the last week I get a really dim screen for most of it but have a band of bright at the very top, about 3/4" is bright. Sometimes the whole screen brightens again, but it doesn't last.

A friend who works in tech repair says it might be a cable that needs to be wiggled back into place inside. I forget the name he used for it.