Yes, it is only a picture. But it’s a picture of you, naked or with very few clothes on, which you are thinking about taking and sharing privately. And there’s no guarantee it will stay private.
So, with thanks again to Thinkuknow, here’s a few reasons why you shouldn’t send that selfie:
Once it’s gone, it’s gone: if someone sends it further, deliberately or even by accident, who knows where it might end up? What if your mum, dad, school friends or teacher saw it?
Bullies go for it: you may have heard stories of teenagers who have been badly bullied because of naked pictures online. If you're being bullied because of an image, you can get help.
It’s against the law: if you’re under 18, it’s illegal to take or share an ‘indecent’ picture of yourself, or to look at or share someone else’s... if it’s naked, a topless girl, or contains genitals or sex acts, it will be ‘indecent’.
You could be blackmailed: if you send a picture you wouldn’t want other people to see, someone could threaten to show everyone else unless you give them what they want.