Nest and my furnace fan - wont stop running

[Link1]

We installed a nest 3rd gen.

id does work for hot at cold but the fan never stops running. 

the fan is turned off, learning is turned off. The fan only stops when we remove nest from the wall.

we have a humidifier which has also been turned off.

there is a blue wire in the wall which was tapped off and not used on the old thermostat.

currently wired like this:

[johnCNA]

Your blue wire is most likely the C wire from the furnace.  If so, it should be connected.  You can verify by looking at where the thermostat wires connect at your furnace.  They are all labelled at the furnace end, too.  Are you absolutely sure the Fan option is turned off in the Nest?  You could try resetting the Nest - press and hold the screen in for 10 seconds or so.  If that doesn't do anything, go in the menus in the Nest itself and do a factory reset.  You'll have to do the setup over again if you use the Factory Reset option though.