I feel so sorry for this little boy....and want to be able to help him?

I've asked questions about this before, but this question is slightly different. It deals with my little cousin Ryan, who is ten. He lives alone with his mom (no siblings) because his father was very abusive to him and his mom. His mom finally left the dad when Ryan was five....after he was hospitalized with broken bones and it was just a terrible situation. he's still learning to trust people, although he seems like any other boy his age. You wouldn't be able to guess the terrible things that happened to him just by looking. I love the kid, but last time I interacted with him over xmas eve I think I may have scared him. He's always been an extremely ticklish kid, and I took advantage of that by holding him down and tickling him until he cried. I didn't mean to do that, or want anything to be unpleasant for him. I think he's okay with being tickled in general...he just as long as it's not on his feet. His feet are ticklish to the point where he doesn't like to walk in the gr...it's very cute. Anyway, one, I'm worried that I acted incorrectly in that situation and am afraid I set back his recovery or something. I don't know how long it takes to recover from what he went through. I guess it's different for different people. Anyway, what I wanted to know is how I SHOULD interact with a child like him who has been through that sort of thing, without resorting to semi-abusive tickling? Like i said, he doesn't mind being tickled briefly on the sides or stomach, but I doubt he likes being held down. What can i do to gain his trust back (if he ever lost it) and should I apologize?