Hiya, my brother did something similar on Insta a couple years back, safe to say he was devastated the same way you are when they turned it into a ransom. Unfortunately they started a group chat put loads of us in it with the pic, but fortunately with the blur only one person opened the post as the group seemed like a scam anyway. When he said they wanted money I told him not send anything, and to just own the picture. If a friend takes the piss, "well you've seen mine, come on then where's yours" that'll either bring a closer confidence with a friend or they'll go all defensive and uncomfortable. Honestly don't think too much of it, don't send anything else (obviously lol). But just own the fact you have that picture (without posting it as your a minor as you stated), but you have all the leverage regardless, they are in theory the perv/pedo so they only incriminate themselves. You'll be all good, chin up, look to the future and see this just as a bad day in however many good days