Pixelating when pushing on screen - MBP w/ Retina

So...I'm a bit overprotective of my Apple stuff - let's start w/ that.

I accidentally pushed my thumb up against the screen and there was feedback/pixelating (not sure what to call it) that went away when I took my thumb off the screen. Going forward, I'll be careful not to put pressure on the screen when opening it - but, is this normal and are there longterm issues to watch out for after doing this?

Thanks for being patient w/ me...