Sometimes people get really bad inflammation at the injection site. This is especially true for people new to IVing. The second time I ever shot up, I had a 2 inch by 2 inch red lump on the crook of my arm that was incredibly painful. I did not miss, and have no idea what caused it.
You should NOT be taking antibiotics unless you have been prescribed them specifically to treat this problem. This is why people get sick so easily; they are unnecessarily fucking with their immune systems by popping an antibiotic at the first hint of infection. Don't do this. Antibiotics are not harmless like most of us have come to assume because of our doctors prescribing them for every little problem we show up with. They have drastic effects on your body and immune system and should only be taken when absolutely necessary and ONLY when prescribed for a specific cause.
As for your inflamed injection site: put a wet wash cloth in the microwave for about 50 seconds or until it's hot, but not too hot that you can't touch it, and press it against the injection site. Hold it there until the cloth has cooled. Do this a couple times a day until it starts to subside.
If it doesn't go way in a week or two, go to the ER because most likely, it has become an abscess and needs to be drained.
Closed.