I solved this by doing something link
$hook = add_menu_page('My Plugin Settings','My Plugin Settings','manage_options','my_plugin_settings','display_plugin_options');
add_action('load-'.$hook,'do_on_my_plugin_settings_save');
function do_on_my_plugin_settings_save()
{
if(isset($_GET['settings-updated']) && $_GET['settings-updated'])
{
//plugin settings have been saved. Here goes your code
}
}