Could be a number of reasons - the first thing I'd check is rear wheel alignment and rear tyre condition & tyre pressure (front & rear), then make sure the fork tubes are true in the triple trees, then front wheel balance, then check for slack/ freeplay in the gooseneck , also you might want to check if the is any play in the swingarm.
I've found in my past experiences with bikes most wobbles emenate from the rear.
a small drop off the sidestand shouldn't do any damage other than cosmetic (woe & betide).
hope this helps
hoffo
