const CGRect imageFrame = CGRectMake(0, 0, 44., 44.);
UIButton *button = [[UIButton alloc] initWithFrame:imageFrame];

[button setImage:[UIImage imageNamed:@"backButton"] forState:UIControlStateNormal];

[button setContentHorizontalAlignment:UIControlContentHorizontalAlignmentLeft];

button.contentEdgeInsets = UIEdgeInsetsMake(0, -6., 0, 0); // здесь получается сдвинуть влево картинку на кнопке, но не саму кнопку

// [button addTarget:self action:someSelector forControlEvents:UIControlEventTouchUpInside];

UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithCustomView:button];

[self.navigationItem setLeftBarButtonItem:backButton];