my newborn's nose has been perpetually blocked for 2 weeks.

Oh dear, sorry to hear that! Sometimes there are just so many reasons why they could get sick/feel unwell, it's hard to pinpoint it especially when it comes to newborns because there's not much we can do for them :/ If it doesn't get in her way too much, don't worry too much about it! You can try to help her by seeing if the environment could be too stuffy/dusty/cold, but other than that I think just clean air circulation would help :) Other than that, you could probably keep the people and things around her regularly cleaned/sanitized just in case - because they get sick real quick so it'll probably be a good idea to pay more attention to hygiene and sanitation if you aren't already. If you are, then you're already doing a great job!