What to do if someone i did wrong does not remember it?

So when i was in highschool i used to hang out with this boy a lot, he was part of our group, the punching bag of the group if anything, i used to said mean stuff to him, in the borderline between stuff you say to your friends and just plain rudenesses, one time i started to say mean things in various of his posts in facebook, he just blocked me, later on we changed groups and we never actually got to see eachother again, recently i had the feeling to apologize, try and redeem myself so i went and look for his account, add him and try to apologize, then he tells me he does not remember me or anything about me that much from the fact we used to hang out, so i am now thinking what to do, i could just say sorry and he won’t understand it, i could try to explain what i did then say sorry but i feel that’s more for my sake if anything, i could try to be his friend again and make an effort in time but this seems intrusive too. So i kinda need advice if i should just leave him alone, even if i feel unsatisfied with myself.