Think about it. You know how sometimes when you feel totally congested, stepping outside on a cold, crisp day opens up your nasal passages in minutes? When you go back inside, back comes the stuffiness. Sucking on a menthol drop helps, too; just the sensation of coolness clears your sinuses.
Of course, if it's the real deal -- you can tell from tissues that your head is a mucus fiesta, and you feel like you're breathing through a mask -- don't let it get worse. In addition to a blocked nose you'll get sinus headaches, hacking and a full-blown sinus infection. (Honey may help your cough, and that sinus infection, too.)
Put your neti pot to work daily. Just fill it with salt water and rinse your sinuses, pouring the water in one nostril and letting it run out the other. If you've never tried this, it sounds weird but it's not uncomfortable. And it works.