Bring it in to the Genius Bar and have a technician take a look. Could be a weird issue with your particular iPad, but nonetheless this is why warranties exist. You may end up getting it replaced!
My 10.5 did that from day 1. I never dropped it. I went into the Apple Store just to see if display Pro models do this, and they all do to varying degrees of pressure. Even the 12.9.
It has to do with the laminated screen, which is effectively attached to the surface glass. Hence pressure on the glass can cause this. This happens mostly at the edge where the home button is located.
+1. Not that I do this purposely on the iPad's I've owned over the years, but I have experienced the same thing from my Mini's to my current IPP. Nothing to be concerned about.