This remedy always helped when I have flu and suffer from blocked nose/runny nose and have difficulty breathing.
Place 2-3 tablespoons of any kind of tea leaves in a large bowl. Then pour in boiling hot water (not warm but BOILING HOT). Pour enough till the vapour starts to come out. Then place a large blanket over your head and cover the bowl. Then breath in the hot vapour. If its too hot for you; lift the blanket a little to let some vapour out but not too much. You will feel your clogged nose opening after 3-4min. If you want add more hot water as the ‘tea’ cools down.
And do not do it too long. A rough estiamtion of 10 minutes will be good enough to clear your nasal passage. Do it three times a day only till the blocked nose is gone for good.