With the engine off, pull the line and 'very' carefully slip it free of the seat on the injector. This is so you don't fatigue the line from bending, they don't take well to that but they aren't entirely fragile either. Slide the nut out of the way and wipe the end of the line clean. A small mirror is handy for getting a good look at the end of the line without too much gymnastics involved.
Similarly, you'll want to check out the seating surface on the end of the injector after cleaning it well enough to see the metal.
On the plus side, a complete set of brand new injectors that are good enough to get you back on the road will only set you back around $200-$250. As I recall, I paid $220 shipped for a set of brand new injectors from a company in Ohio. I did this as a matter of course shortly after I bought my m1009 and they have lasted more than a year with much of that time spent running WMO. I saw a vendor on ebay selling individual lines for nearly sixty dollars each, but I'm sure you could do better at a junkyard or other venue.
Either way, you won't know what you need to to do until you get a good look at your problem first. Might be that you just have some gunk in the way or something.