Bizarrely I did a 2 day study at Kings this month on Immunisation and Vaccination and the lecturer said that a red injection site is actually a good thing. It shows that you body has responded to the vaccine and has naturally produced its own antibody response. The same thing that its also good news that you may get a little 'man flu' not long after having the vaccine. She said this was a healthy response.
Ive never produced either- and was rather disapointed when I heard this! Im abit of an antibody failure based on that....
However, if it is coming up as somethign that looks angry, red and pussy I would imagine it would be an infection and certainly worth getting an eye cast on it. Especially if you end up with a fever. Have you tried a couple of paracetamol, might knock the whole thing on the head?