Good call mate - MUCH better safe than sorry.
Also a good idea opening the door and windows - a good friend had carbon monoxide in his TB10 while on the ground once. All ocupants were ok, but if they'd been in the air.....
IMHO, it also wasn't a good example on the instructor's part to fly with a blocked up nose - any form of cold can be very dangerous even 1000' up.
Happy Christmas to all,
tKF