Part of the social contract is forgiving people so we can all move forward. I don’t think you can go back and say something was not ok retrospectively after having said it was ok, without breaking that social contract and going back on your word…but next time you interact with the person you can ask them not to do it again.
There isn’t much point in dwelling in the past and relitigating it, just work on making the future better without causing trouble.
Ex: Branda, it’s totally cool last time, we all understand, no worries about it. But please don’t get drunk at the next party on Saturday, we have to set a good example.
I think it depends on the thing that was done, whether it harmed someone, and if it harmed you. You wouldn’t want to say, “it’s cool you hit me and broke my nose” even if you forgive them, and especially if the reason you brushed it off before was out of fear of escalation. In cases of harm, they’ve already broken the social contract.
People-pleasing and excessive conflict avoidance. Been there before.