Look up: Underage Girl Scam on the internets. Also known as The Badger Game. Were you on POF by any chance? Some other website? That is how these usually get started. The current versions have a guy call you who says he is a cop, but the truth is they are just criminals. There is no warrant for your arrest.
This is blackmail, extortion. Go to your police. If you did send photos, if you have been messing around, and are scared of being exposed to wife, family etc, you will just have to tell the scammers to [***].
Contact YOUR police department - that is EXTORTION - a crime. Don't pay anything or even talk to the scammer. There are many other similar posts fron the 803 area code.