Why is the bottom left of my Samsung J3 Emerge (2017) dark and different from the rest of my screen?

[Android Central Question]

I got my Samsung J3 Emerge (2017) in October 25th,2017 and had zero issues and everything was good until today where the bottom left of my phone was dark and different from the screen and was wondering what caused this because it's just the spot that bothers me but the phone is still alright and functional.I assume it's because I bring my phone into the shower to play some music while Im showering but it has a case but I'm unsure how it could've happened if I've been bringing my phone everyday from the day I got it and haven't had any issue.I tried powering it off and putting some pressure on the spot but it doesn't want to go away.Is this a device issue,screen issue,or a temporary issue?Someone please explain.