I think you did exactly the right thing, as much for the other kids' sake as for your ds.
Little boys that age do get carried away at the end of last term the reception teacher took me aside after school to say that my ds had (apparently) gone up to another boy in the playground and kicked him in the stomach. Both she and I felt that it was out of character for him, and I never really got to the bottom of why he did it I suspect he was just showing off and made a bad call about what constituted an acceptable level of boy roughhousing. Conversely on a different occasion ds was bitten by another child, and the school also took it v. seriously, making the offending child write him a letter of apology.
I was entirely happy with the way the school took these incidents seriously. I think little boys are thoughtless sometimes and make errors of judgement, but if they don't have these boundaries spelled out to them, they'll carry on thinking this is ok. At this age I don't think they do label each other for 'telling' -- that comes later.