is it still there if you remove the screen protector? if not, replace the screen protector.

Yeah, that'd trigger me too. I'm sure there's a "way" to replace the case (i.e., buy a broken phone but pristine case and do a transplant), but it all depends on the cost and trouble you'd want to go through. Might be cheaper to just buy a slim clear case or vinyl wrap and at least it'd cover up the blemish for the remainder of ownership. I assume you went OG naked for a reason, so the case/wrap idea is a compromise.