Horizontal line on display screen

I’m using a MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports) for a year now. Everything is working fine until earlier today, I noticed there is a really thin line on the bottom part of the screen.

I tried restarting my laptop but even on the process of that it still appears.

Looking closely, it seems that the thin line is actually part of my current wallpaper.

Please help me figure out what’s wrong with it. (Is the problem the screen itself or is it a system/software thing?)