Rabies vaccines are killed, adjuvanted vaccines. Adjuvants are inflammatory components (like aluminum salts, which are known carcinogens) added to ehance the immunological response -- a human equivalent is the tetanus vaccine. These cause swelling at the injection site.
Personally, I would watch the site carefully to make sure the lump goes away, if it does not, have a needle aspiration done in several spots. You should notice it starting to shrink.
If you go to this link,
http://www.yorkietalk.com/forums/yor...ions-dogs.html , you will note that 19.4% of the adverse reactions reported to rabies vaccine manufacturers were injection site swelling or lump.