Doubt you did any harm and was probably just hearing the rattling of the throw out bearing or gear assembly in the tranny. After something like that happens, you'll naturally be more paranoid and hear all sorts of 'new' things that probably was there before and you never noticed.
BTW it sounds like you just went into neutral, not really a misshift in the traditional sense. If you went into 1st, then that could've been a bad thing but how bad would depend on the speed you were going at the time and how fast you reacted.
Just a general test for anyone interested: drive your car really hard ripping through the gears. Warm things up real good. Make several passes if possible. Then park in a nice quiet place (preferrably at night when there's less traffic, noise around) roll up the windows, clutch out and just listen. You'll hear all kinds of rattling crazy sounds coming from the tranny. Push the clutch in the everything disappears. All pretty normal and nothing to worry about unless the sounds get unusually loud.