Steam, Bobert.

Fill a large bowl with boiling water and snuff up the steam. If you have some oil of wintergreen about the house, add a drop to the bowl.

If that helps, you might consider moving on to the advanced class: Snuffling Salt Water. This requires a small dish of warm salted water, or you might try a Neti-Pot if you feel the need for purpose-built kit. Close one nostril with your finger, and dip the other into the water, then sniff gently, pulling a little water up into your poor, clogged schnoz. Don't drown. Blow it out into the sink and repeat on the other side. Do this three or four times a day.

Don't forget to clean the sink ...