Can I lock my PS4 console from somewhere else?
There is no way you could remotely lock or logout your PS4 console. As doing so would be directly result in Hack attempt. But you could try changing your PSN password which is used on store.playstation.com. That would log out the user from the console and he would require either the new password to login or would need to create a new account.
However he would still be able to play games with his new account after logging into that console.