Young and Thin... but Loose Neck!

Hi! I'm a young and thin male. I used to be fat a few yrs ago, and I've lost a good amount of weight since then. My ribs, show so I'm kinda too skinny right now haha. Well, i think that maybe my neck (specifically under chin) skin is flabby due to my past chubiness... so didn't tighten like the rest of my body. Does anyone have a suggestion on toning and tigheting my neck/under chin?

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