You've made the right choice. Sending pictures of your private parts to a stranger online is NEVER a good idea.
Even if you think you know the person you are chatting with, they may not be who they say they are.
Pictures of your private parts might be used to bully you, get money out of you or make your life miserable. They may be shared without you knowing.
You should always remember that if you send a picture online, it is almost impossible to get it back or prevent it being shared.
You should now tell a responsible adult what has happened. You could tell your Mum, Dad or Guardian. You can also contact the Police on 101. You should never feel embarrassed about telling an adult about this. We only want to help keep you safe online.