You can hide your button by which you have made your barbutton ....
UIButton *button1=[UIButton buttonWithType:UIButtonTypeCustom];
[button1 setFrame:CGRectMake(10.0, 2.0, 45.0, 40.0)];
[button1 addTarget:self action:@selector(showLeft:) forControlEvents:UIControlEventTouchUpInside];
[button1 setImage:[UIImage imageNamed:@"anyImage.png"] forState:UIControlStateNormal];
UIBarButtonItem *button = [[UIBarButtonItem alloc]initWithCustomView:button1];
self.navigationItem.leftBarButtonItem = button;
[button1 setHidden:YES];