Black smudge on bottom screen only in locked mode - retina 2014

Mine is a MacBook Pro (Retina, 15-inch, Mid 2014) 2.2GHz with Integrated display. When I opened the laptop this morning, I was welcomed by a locked screen and noticed a black smudge on the bottom portion of the screen. My heart sunk for a moment but when I logged in, I didn't notice the smudge any longer.

I see the black smudge which looks like an ink blot (see pictures below) when I go back to locked screen again. Is this a failed LCD or could there be something else going on? If it is a failed LCD why don't I see the problem when it is unlocked? Why would an LCD behave differently in locked and unlocked modes? How to fix it? Thanks for any help.

Unlocked Screen

Locked Screen