Children and young people love to share their lives with friends. This could be funny and amusing, but sometimes could cause big problems. There is nothing bad at sharing images or videos of your own with other people, however children should be cautious. There exists the risk that the photos you publish are not appropriate and can be used against you with or without intention and consequently affect your whole life in the present and maybe even in the future.
As a result, parents have a holy role to help children act carefully in online relationships. They should be warm and calm when discussing topics like online sharing especially when it comes to naked photos.
If the situation goes out of control, there are some handy resources such as Internet Watch Foundation and NCA-CEOP. Do not forget that naked photos of children under 18 are prohibited in social medias and if this happens it may constitute a criminal offence.