WordPress Plugin Localization

The filter comes with the text domain as second argument. So you could do this:

function wpdev_170138_plugin_locale( $locale, $domain )  {

    if ( $domain === 'myplugin' ) {
        return get_option( 'jezik' );
    }

    return $locale;
}

add_filter( 'plugin_locale', 'wpdev_170138_plugin_locale', 10, 2 );

Now only your plugin’s locale is changed.