It does require some additional coding on your part if you're up to the task...

Here are the steps I would use:
- Replace the existing widget with a mere placeholder, e.g. <div id="fbLikeWidget"></div>
- Request user consent (similar to cookie acceptance notifications)
- Set a cookie for the user, e.g. privacy=yolo
- Use JS to read the value of that cookie and if it's set to "yolo" (you get the idea), inject with JS the FB widget into the placeholder of the first step.

It's out of the scope of the support we provide here. And it's also something you'd apply to a site entirely, so it can't be part of K2 only.

The following is standard Joomla template overriding stuff...

First, learn how to copy K2 source template overrides into your Joomla template by reading this: getk2.org/documentation/tutorials/174-templating-with-k2-and-the-concepts-of-sub-templates

After you copy the files into your Joomla template's html/com_k2/ folder, edit the file html/com_k2/default/item.php - that's the output of the item specifically.