Your school will have ways of dealing with these sorts of problems and can confiscate mobiles if they believe they have sexual images on them.
Sometimes you might be added by a username that you don't recognise.
This can make it hard to tell if you know the person or not.
Try having an honest conversation with the person you sent the image to. Getting help The sooner you talk to somebody about the situation the better.
This could be your mum, dad, carer or a school teacher.
A good idea might be to set up Snapchat so that you only receive messages from people on your friends list.
You can do this by going to your settings then going to ‘Who can send me snaps’.
But it’s important to remember people can still take screenshots and save them.
Then they’ll have a copy of your picture on their phone or tablet and that means Snapchat can’t delete it.
When you’re under 18 it’s against the law for anyone to take or have a sexual photo of you – even if it’s a selfie.