Hello Welcome in H.C.M. I have gone through your query regarding vertigo with severe earache after strongly blowing nose by your son. On blowing nose against close nostril always increases venous return to heart because of increase in intra abdominal pressure. This in turn causes engorgement of venous system which you have seen as blue thick vein behind the ear and gradually that became fade in due course of time. Other very important thing is that this also pushes air in middle ear through eustachian tube. Very rapid gush of air in middle ear exerts pressure over tympanic membrane and some times this may lead to rupture of ear drum, and at the same time this may also pushes to stapes which results in vertigo. All above are self limiting and heals well. I hope your query is answered. Regards.