I feel a lecture about not being rough, what is expected of him in school and no tv for the day. Is suffice. Specially if you and the teacher feel that he was just playing with the other student.
I agree, a simple punishment is in order. But relax, he obviously understands that he hurt his friend and that made him feel bad. I would worry more if he showed no concern.
yeah, i would do something like when he's ready for bed, go sit with him and talk with him about it, that he knows he's not suppose to be horseplaying in line or whatever and basically just remind him of when its appropriate to play- outside or at recess, you know? i'm sure like it was stated earlier, he feels bad as it is. poor thing :)