Don't run through it. I had knee pain a couple of weeks ago and have now pulled out of the half I was training for on the advice of a physio. My IT band is too tight and the knee was taking the brunt. I'm having twice-weekly deep tissue massage (OUCH!) and have been told not to run and certainly no cross-training. Lots of stretching is required. One event isn't worth long-term injury...better to get it sorted and look at the big picture.
I ended up ditching Nimbus and going with Saucony ProGrid Triumph which I'm really liking. Walked around in them for a day and then took them out for a trot - very comfortable and probably prefer them over the Nimbus.
Ah, the left knee...I've just been told to stop running for a little while after I went to a physio with my sore left knee. It turns out the knee isn't the problem, it's my IT band. Have been going twice a week for deep tissue massage which makes me whimper in pain. Might be worth getting it checked out, as I ignored mine and am now paying the price.
I have asthma and run...I've found it's taken a while but my asthma has become less of a problem the fitter I've become. At the beginning I had to run with the blue puffer and take it regularly whilst running, but now I tend to run with it just for the security blanket value. I'd agree with checking with a GP. There are so many varieties of inhalers it's best to work out the combination you need.