Unfortunately, Monsoons are crap! If you can take it back, I would. I have one and am on my third unit because the timers eventually quit working and will spray whenever and for however long they want! So even with all those extra nozzles, I have four left that barely work. I am saving to get an aquazamp in the near future.
I don't really know of an effective way to unclog the nozzle. If you can force water through it somehow with a syringe? You can't really do anything with the hole because that will screw it up as well.