With motorcycle helmets, even if you just drop the helmet from waist high, it should be replaced unless inspected by the manufacturer. Reason being that the foam deforms even from that height, and it will not protect your head as designed.
This sounds pretty equivalent because of the weight of the bike, so in good faith I can't recommend you do ANYTHING other than full replacement or inspection by manufacturer.
Another bit of motorcycle knowledge: What is your head worth? In the case of my motorcycle helmet, $600! I bet you your bicycle helmet is much less, and so buy another!