Idk whether this is OCD or if I should actually feel bad. During the George Floyd protests I can’t remember if I might have re posted a video where a protestors face was visible on my Instagram story. What if I did ? I cannot remember. So if a racist person hunted them down and killed them , or if a cop killed them it would be my fault .

This is a good time to practice exposure without engaging compulsions.

Well, it sounds a lot like scrupulosity obsessions I've had. Not remembering whether I did something, but it feels like I might have, therefore if I did then I would be responsible for any bad consequences, so it's also my responsibility to try to prevent consequences from happening, and take responsibility for anything that might happen. All I know is that trying to figure it out if it happened makes it feel more realistic, and that trying to right a wrong which may not even have happened is a bad idea- whether it's by posting an apology or looking for the post to remove it or even just punishing yourself in your head. You used the words "should feel bad". My question is what good it does you or the world for you to feel perpetually awful about something you can't change? Feeling bad is ONLY useful to the extent that it affects your future behaviour. That's the whole entire purpose of feeling guilty. It's designed to teach you, and then pass. When something is done carelessly or accidentally, we usually feel less guilt, because the only purpose the feeling serves is to say "pay more attention next time". You already know that you are going to do your best not to post something like that in the future. You can operate your moral compass perfectly well without your OCD bullying you and without you deciding that you ought to feel bad. You feeling bad would not serve any purpose or change your behaviour or 'be justice'. Therefore, you don't need to know the answer to this question in order to know whether to spend your time suffering. Decide not to suffer: think about something else.