Congratulations on your 10K.   That is indeed awesome!!!!    I have periodic numbing of some of my fingertips, sometimes when they get cold while I'm running and sometimes when I"m in the house at the desk..... so I've had that phenomenon and I don't think it has a thing to do with the running and cannot be much help as to what causes it.  I think it is called neuropathy.   But, it would be worth running by your doctor - that is what I plan to do at my next appointment.

Again, congratulations on your 10K and on your fabulous progress (and weight loss!) in 2010 and continuing.  Keep up the great work and hold on to that sense of awe!   I find that, as I lost the weight and was able to do more and more, I too have frequently been in awe over being able to do these things!  

Hooray for you and you should be very proud! 

Check your breathing.  Sometimes if a person hyperventilates it can cause numbing/tingling in extremities.  A good, easy way to make sure you're breathing right is to count breaths on your steps.  I would suggest breathing in sets of 3: 3 in and 3 out.  Avoid even numbers because it can cause cramps and soreness because you always start inhaling and exhaling on the same foot.  Crazy, but true.