Thank you for your query to DoctorSpring.com
I can understand how recurrent nose bleeds may be a source of concern.
However there are a few aspects of your history which is reassuring of the fact that the nose bleeds are NOT due to a serious etiology. Also since you have not mentioned a history of easy bruising or bleeding from gums or familial history of bleeding disorders it rules out such things out.
The quantity of the nose bleed which in your own words is a very very small amount and the fact that an ENT examined you and found no serious cause is reassuring of the fact that it probably due to the change in humidity. Nose bleeds are common in extremes of temperature either in the external temperature or inside heating or air conditioning. Therefore I wouldn't recommend any drastic measures right now except to use a humifier to moisten the air and see an ENT only the quantity of the nose bleed is significant or prolonged.
Hope this helps, feel free to discuss further