Last May I got a cold (slightly blocked sinuses) right before my last pool session for OW cert. I was given a lot of advice from "don't even go in the pool" to "take sudafed coupled w/ swimmer's ear", etc.. Here's the thread for reference:
http://www.scubaboard.com/showthread.php?t=98587
Me, being overzealous coupled with having plane tickets in hand, hotel reservations, a car rental, and referral reservations with a dive op in the Keys pushed me to taking the latter advice.
Bad mojo, man. I ended up with ear barotrauma that kept me out of the water for over 10 months.
I feel your pain, but it isn't worth the risk imho having been in your situation myself and ending up having to wait almost an entire year to get back in the water because of one stupid mistake.
Now, if your sinuses aren't blocked (or partially blocked or starting to block up) then that's another story. Maybe you could get by with the suggestions above. But if it were me...which it was...I wouldn't do it.
Best of luck to you!!