Update: A few days ago we crossed paths volunteering at an event, and while it felt like we were not connecting super closely, it wasn't weird; it was a huge public event, so it felt appropriate. Today we had a breakfast meeting, one on one, about a project we are working on together (he works for one of my clients), and we connected personally as well, and everything felt normal and good. It was a very good lesson for me about what it feels like to make a mistake, apologize, be forgiven, and move on, all in a fairly short timespan. In the past I would have spun my worry-wheels for weeks or months afterwad. But maybe it really is effectively behind us.
In looking at the situation, I don't think I made any grave error, I think I just mis-predicted his personal sensitivity about the thing that came up, and now I know to be more careful around that topic with him, and to be especially mindful of supporting his feeling of security/privacy in public.
It also brought up a number of issues for me that I was able to take to my therapist this week and also work through on my own, broader things related to anxious attachment and my relationship wounds and so forth. So it was a helpful experience, if painful for me (and him). I'm not feeling like I need to process with him, unless it happens to come up at some point, but it doesn't feel necessary to bring it up.
Thank you all so much for your thoughtful responses and caring perspectives right at the moment when I needed them. It's much easier to grown with help and support.