Black line where screen is cracked

Just noticed a really small black line on my iPhone XR. The screen works perfectly fine otherwise, but it also looks like (when the screen is black), that black line is like a crack (appears like glass there is broken). I am using a screen protector but I'm worried it's affecting the actual phone screen underneath, bc that black tiny line is showing up.

Is it the light reflecting off weirdly, or the glass creating a shadow that's causing this weird tiny black line?

If it isn't, and the lil black line is affecting the actual phone screen, should I immediately replace the screen? Since it'd be a problem with the LCD screen, most likely it'll be fixed by replacing it.

Can I just leave it there, and then maybe in a few months replace the LCD screen if it actually gets real bad? (I really don't feel right about spending money to completely replace the screen for a tiny line that isn't even doing anything, so unless it gets real bad, I don't want to spend that cash. I'm just wondering if I can get away with not immediately replacing the screen).