Signs of infection:
Increasing pain, increasing swelling and redness, fevers, chills, malaise (feeling sh*tty).
Responds to antibiotics.
Signs of abcess:
All of the above, plus severe pain and fluctuance (a "tightening" of the skin and soft tissue due to pressure from a pocket of pus--usually very red and very swollen).
Requires surgical drainage.
You don't seem to really describe any of this. Probably just a local reaction to the injection.