Screen appears with grey/black bars across it that come & go.

My laptop was dropped over a year ago and had been working fine until a few months ago. The front left corner (when sat closed on a desk, facing you) was dented but everything worked fine. However, now there are sometimes grey or black horizontal lines that appear on the screen (each about 2inches thick). For a while I could wiggle the screen and the lines would clear but now here is a dark black line along the bottom quarter that won't budge. I have taken a screen grab and the image doesn't have the line so it is just a display issue. I am guessing there is a connection issue but don't know for sure. Help please!!

Adam