Other than post an apology that doesn’t surrender to guilt, just accept this as an unfortunate feature of serving the public and return your focus to your continued good work.
Unless you’re receiving a lot of negative reviews, and you’re probably not, then there’s nothing to worry about. Most readers can tell a rare and unqualified complaint when they see one, so it’s unlikely your business will be affected.
We all are subject to bad reviews. I got my first after many, many years of 5-star comments. It was a small thing blown up to a catastrophe, as they often, are by a client who was feeling mistreated somehow.
We can’t argue someone’s personal reality, but we can minimize the damage and time spent in turmoil over what we can’t control.
Better to move on and make sure you’re treating all clients with the attention and excellence they expect.