I must have been lucky so far that I've not had need to discipline DS who is 2 and 3 mths, but today he stamped on another child 
I had NO idea what ti do, I held each arm so he couldn't run away and said firmly 'that is very naughty, do not do that. Say sorry to friend'
He ignored the first bit and refused to say sorry
With hindsight perhaps I shouldn't have tried to get him to say sorry when it was unlikely he would thus he 'won'
What should I have said / done? I was all flustered and confused and gave a really bad impression to the other Childs parent, plus DS didn't seem to take on board the telling off, he was a bit oblivious.
Help. I can't have a badly behaved child, which I'll end up with at this rate