can Apple tell if spot on screen happened before or because of dropped phone?

I recently noticed a white blur not quite in the center of my iPhone 6. It is most noticeable when the phone is on and the screen is all black or dark colored. It doesn't interfere with anything, at least I haven't noticed it interfering with anything. After I noticed the white spot my 4 year old son dropped my phone on the sidewalk and slightly cracked the screen in the upper corner mostly, not anywhere that the white blue is. My question is this, can will Apple be able to tell if the white spot was there before the phone was dropped or if the drop caused the white spot. I would like to send it in for service I just don't know if it will be covered under the limited warranty. Apple will send it back unfixed if you say it is to be fixed under the warranty and it ends up not being covered. If the spot isn't because the phone was dropped it should be covered, if it is because of the drop I don't believe it will be covered. Any input or advice would be very much appreciated! If you take the time to respond than you are a totally rad rockstar and you definitely will be my superstar of the day!! Thanks so much!!

XOXO