Does he do this at home? If not then why punish him at home for it? In fact why stress over it at all, if he's fine at home go back to enjoying your time with him. Put all his toys back, wipe the slate clean and start again...guilts no use in resolving problems.

He's not a bully, he simply hasn't learnt better ways to comminucate his feelings yet...and he's a boy, boys kick, hit, shout, spit...etc etc, its NORMAL. Worry when he sits quietly and doesn't react to anything.

What do nursery do about it? They need to be the ones handing out consequences and your part is supporting them in doing so. You probably need to go in and speak to them about it and work out a plan your all happy with