From our program rep, in answer to my query about what to do:
I know you want to run this weekend but I strongly recommend against it. It's much more important for you to rest and heal completely before tackling this distance. Remember, there is no single run that will make or break your training or marathon performance. We have a 26 miler coming up and if you do 23 instead, you'll be more than ready for race day. I also recommend you stop running altogether for a while. At least until this clears up.
Sucks the big one.