kinnamon32, let me throw in my two cents on this issue:

First off how does the knee actually feel?  After a fall like that, I would expect you to have some lagging aches and pains.  If all is well I guess the priority would be the New York Marathon.  I am not sure when it comes about, but it also sounds like you may need to rest the leg a little.  Doesn't sound like it has had enough time to recover.  I have heard of a few people who can run marathons every two weeks or so but I guess it might be a bit tougher for you due to the injury.  However, since each of the races is two weeks apart, which I guess means at least two of the races are 4 weeks apart, maybe you can at least run two.

Whatever you decide, good luck on your races! 

The good news is that you can defer NYC this year and run it next year if need be.

With respect to your knee it depends on what is wrong.  Since you have run on it with no problems and you didn't think it was bad enough to go to a doctor then you are probably good to go.  But I'm an engineer, not a doctor, so take my opinion for what it is worth.  My thinking is that If there is no major bone or tissue damage and the swelling is gone then that's great and you can enjoy NYC.

Good Luck