after checked the checkbox in backend, dont show social link on frontend

Question

It cannot be in post metabox, because it is site setting, not specific page. You can create submenu position for settings in your admin panel by add_submenu_page function, for example:

add_action('admin_menu', 'add_my_settings_submenu_page');
function add_my_settings_submenu_page() {
    add_submenu_page('options-general.php', 'Page title', 'Menu title', 'manage_options', 'my_settings', 'my_settings_submenu_callback');
}

Then you need to create callback for last argument where will be all logic of your code. This should be something like this:

<?php function my_settings_submenu_callback() { 
    if (isset($_POST['disable_footer_social'])) {
        update_option('disabled_footer_social', $_POST['disable_footer_social']);
    }

    $option = (bool) get_option('disabled_footer_social', false);
    ?>
    <div class="wrap">
        <h1>My Settings</h1>
        <form method="post">
            <table class="form-table">
                <th>Disable footer social buttons</th>
                <td>
                    <input type="hidden" name="disable_footer_social" value="0">
                    <label>
                        <input type="checkbox" name="disable_footer_social" value="1" <?php echo $option ? 'checked="checked"' : ''; ?>>
                        Disable
                    </label>
                </td>
            </table>
            <?php submit_button('Submit'); ?>
        </form>
    </div>
    </table>
<?php }

In your footer you can check if this option is checked by get_option('disabled_footer_social'), for example:

if (get_option('disabled_footer_social', false) != 1) {
    // show your buttons
}