I found a trick somewhere on the net for clearing a blocked nose (even very blocked). Hold your nose, inhale deeply, then repeat tipping your head back for four seconds, and then forward for four seconds. Breath out slowly. Then hold your breath as long as you can, still tipping forward and back every four seconds and holding your nose. Eventually you inhale and all the gunk just sort of flows out of your nasal cavity. Warning... much gagging, spluttering and spitting at this point. But it's worth it.