I've got a number of friends who don't use social media. I don't see anything concerning about it.
As far as applying for jobs goes, I use my FB privacy settings, so no employer could look me up anyway. Frankly, as a potential employer, I'd be dubious about someone who didn't use their FB privacy settings. Likewise, if was online dating, I would still keep my FB private.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.