This works for me.

blow out all the air from your lungs.

hold your breath and pinch your nose.

exhale more air (and more and more)

attempt to breath in through your nose (against the pinch)

hold your breath even longer.

(optional aerobic activity to use up the last oxygen (pushups, running))

when you can't hold any more (hold a little longer)

Physiologically internal parts will constrict to open up the airways.

Finally release the pinch and inhale only through the nose.

(airways open; ears pop, mucus loosens)

I went to an allergy doctor (covered by insurance), got the tests, and found out I'm allergic to dust mites. Since following the doctor's advice, my nose no longer gets stuffy. Stopping the chronic inflammation has also helped my overall health and will probably prolong my life.

It was straightforward: encase mattress and pillows with waterproof covers (SafeRest & AllerEase), launder all bedding once a week on the hot/anti-bacterial setting, switch to furniture with non-fabric upholstery (Ikea Knislinge), and move to an apartment without carpet. Sleeping with a window open has also helped me a lot.

Ask an allergist. It's a common problem.

Mine used to be as well. Turned out to be some sort of allergy, most likely a gluten intolerance. I don't eat gluten any longer and my nose is rarely, if ever, blocked.