To admit that you were wrong or did not act well at a certain point in time is not an easy thing to do. Overcoming yourself and your pride, admitting a mistake to yourself and others. Not everyone does. And not in every situation.
I believe in sayings of the kind “better late than never” and “it is never too late to be the person you would like to be” (even though I don’t remember who said those first). It might take some time, but it is still worth saying it, if you came to realise you did a mistake.
Without going into detail, I recently experienced that when someone was telling me after months about being unhappy with the own behaviour and expressing the wish to explain it. It did sound like an apology. I appreciate that.