Put pressure on the person to remove the message though their peer group and carers.
Tell a trusted adult about what is happening and explain the situation, they might have advice tailored to your specific situation.
Report it to the social network
If appropriate then tell the police
Explanation:
Start up a dialogue with the person to find out if they would be willing to take down the message, and find out why they did it as this could prevent a similar situation happening in the future.
Applying pressure though their peer group to conform to your standards is also a good measure to take as they would not want to feel left out.
If any images that you have taken are being shared then you can try to have them taken down under copyright. If personal information was shared then did that breach the laws in your or their jurisdiction?
