Chewing/licking paws is the cardinal sign of some kind of an allergy...flea, dust, grass, pollen, food, whatever.
-- Did you switch foods at all recently?
-- What was the "shot" given...steroids...?
-- Is the skin irritated where it's patchy?
If it is indeed allergies, I'm very surprised that the shot (if it was steroid) hasn't provided any relief at all - that's very odd. Or did it give relief at first and then wear off...?
For year-round allergies, your best bet is either Apoquel or Atopica.
Read more about allergies here:
http://www.yorkietalk.com/forums/die...tart-here.html