I would attempt to visualize all of the cold (bacteria/virus, I can't remember what it is!?!. Wait, I think its a virus. lol. ) imagine them like particles, wherever you want them to be. I would then probably visualize some type of energy, wheter it be white, green, blue, or whatever colour you think of when you hear the words "healing energy" next, imagine them kind of wiping out the cold particles, maybe in a type of wave, or maybe surrounding individual particles, and overriding them.
Meh, hope that helps, it probably wont work, but its worth a try
Also, aren't there some pressure points that can relieve blocked noses?