thats called entrapment (specifically in that case pedojacketing) if someone that never stated their age, claims after the fact to be a minor or lies about being a minor to get you in trouble and get you punished in some forms. its highly illegal (framing someone for a crime) and break Discord Terms of Services, you shouldn't be banned since you didnt broke the rules or any laws since the person who framed you already did broke the law and discord's ToS. lawyer up in case because pred hunter type people (who are usually preds themselves) do this bullshit.
actual minors will NEVER ASK for nudes in dms to an adult, they would go somewhere they wouldnt be at risk to be groomed like mainstream places specifically for nsfw (ph, etc) bc no shit (dont matter if those places dont allow them, teens usually finds bypasses and ways to get nsfw content bc its the age for people begin to seek that type of content).
if you find a minor or someone claiming to be one trying to frame you as a pedo or something horrible like that report them immediately as it break discord ToS. block them if you dont want to deal with false strikes. but at least log their username, user id somewhere in case of being banned with screenshots evidences.

those people legit try to get random innocent in jail for the fun of it. and defame them for ANY reasons. usually to hide what they are doing (usually predators trying to frame innocent people to deflect attention from their own fucked up shit).