I'm 17 and this guy said he was looking for models and he lied and he ask for some pics and now if I don't send him more dirty pics he put them all on the internet and he won't delete them what should I do?

There is very little you can actually do, except reporting him.

I guess

You report it to the police, what he is doing is a common scam. I will assume you are not a minor, if you are a minor there are even more law broken.

But report to the police is all you can do

Ok x

I know it is bad, but first and foremost stop talking to him, and don't give him any more photos, each time he will want more and more,

Next report him, and try to help get him arrested, you may not want to tell others, but you may save someone from worst by stopping him

The definition of "dirty pics" matters here. If you are under 18 and the pictures involved a sex act, then that is child pornography and is illegal. The police will care. If, the pics are just nudes, then it is not necessarily illegal and the police may only care in terms of it being extortion.

In either case you need to swallow your pride and report it.

I'm 17 and this guy said he was looking for models and he lied and he ask for some pics...

In what way did he lie?