This isn't anything to mess w/ man...
I've seen 'someone'

hospitalized and operated on b/c of an injection causing a staph infection that got out of hand...
First off, DO NOT inject in the same area!!!
Secondly, have you noticed this symptom in any other inj areas from the same gear?
Now these guys above could be totally right. It's quite common to get soreness and swelling from high BA/BB gear that is harmless and will go away.
However, getting ahead of an infection the best way to insure a non-surgical resolution.
It's really impossible to say either way w/o examining it, but the fever and hotness as well as swelling at the site don't sound good (especially the fever).
If it doesn't clear SOON, I'd save yourself a whole lotta trouble and have a doc give it a look. Tell him it was a B-12 shot or some such bs. Usually a course of anti-biotics can clear it right up if it does happen to be infected...