Awkward encounter with ex situationship

So last year this guy who’s 2 years younger than me asked for my number and we talked for like 4 months until I decided to cut it off. We met each other at school and continued talking during the summer but we never hung out. Every time that we had plans to hang out he would leave me on delivered for four days and come back with a crazy excuse like, “I fell down the stairs”, “my dad got a heart attack” , “my brother is moving” etc. and this was EVERY single time. I decided to cut it off bc it was disrespectful for him to stand me up like that and not keep me in the loop especially when something crazy like that happens (if it even happened). Then I blocked him bc I was really hurt and he had left me on delivered for about 2 weeks. Fast forward to a couple days ago, I bumped into him at the pool and he came up to me (with his friend) to talk to me except I felt like I was being kind of rude bc he asked me what I was doing and I said, “just leaving”. I felt uncomfortable and shocked to see him there, especially since I was wearing a revealing swim suit. But then we asked each other how we were and everything was fine and as we were talking I really was getting ready to leave bc I had to go home. As I was walking he went the other direction without saying goodbye and so I said, “alright bye then!” But now I feel really bad bc what if he was just trying to make amends? What if he knows that I blocked him (on messages)? I forgot how much I had liked and cared about him, once I saw him all I remembered was the pain and anger he caused. I unblocked him but I don’t know if I should send him a short, “sorry if I seemed kind of rude the other day” or if that would be like ruining my dignity or something by apologizing to a dude who ghosted me. But he really cared about me !!! Aahhh I don’t know what to do pls help !!