If your website is good at mobile friendliness then just ignore the message. The mobile-friendliness of your site will effect the serarch results of your website in Google now.
Due to the increased usage of mobile and tablet devices in internet world, Google has forced to change their old search engine settings. That's why they are displaying the message to everybody. If your site is compatible for mobile, then there will be no issues if not you should check your site coding and work on it for mobile-friendliness.