Ex threatening to post my nudes

I sent my ex nudes awhile ago we were together for awhile and I trusted him. Now he says I'm being a bitch and he posted one of my nudes on Instagram and tagged me in it I immediately blocked him (we don't have mutual friends) and I apologized to him and asked him to pls pls take it down he took it right off and now he's basically saying if I don't do what he tells me to do he's going to post all of them. He's basically threatening to post them if I don't come over and sleep with him. Like I don't know what to do someone pls help! He's a psychopath.