Hi spontaneous sunflower,
You're not the only one! All over Australia (and parts of the world), as people come out of lockdown they are finding themselves in the same puzzling situation you are in: having the legal freedom to get out and about again, but anxiety about doing it. I've been struggling with it every day so far, and like you say, just feeling more sensitive in general about my other insecurities.
My best guess is that socializing is like a muscle, and when you let it get a bit weak or atrophied you're hesitant to use it again. Slowly but surely as you exercise it (go out, see more people, return to social life), it will get stronger and start to feel like second nature again.
In regards to the incident you referenced from the other day, that is obviously completely inappropriate behaviour and a violation of your personal space (during a pandemic no less!). It's no wonder at all that it's made you even more anxious about going out, and no doubt it was a reminder of some of the less pleasant aspects of public life that you simply don't have to deal with at home. I think the advantages of having a controlled, contained environment at home have been come familiar and comfortable to all of us, perhaps a bit too much.
Recognizing that you're self-isolating puts you miles ahead of the pack in terms of getting yourself back to normal. Just gently try to notice when you're doing it, and simply take a walk, set up a small, low-pressure get-together, or some other brief outing. It will come easier in time, it's been a wild experience for everyone.