I wouldn't touch antibiotics if you do not need to. If you are worried about saving money so much, I would just stay off of gear. You can be honest with your doc, he will probably think your an idiot and most infections from gear now are from improper pinning procedures. Do you have a pic of the site?
The problem with anti-biotics is if taken to much or if not needed, they can stop working for you. Or even mess you up even more. Best advice is to never self diagnose your self, a friend of mine took test p tren a mast blend and thought he got fucked up cause he could not walk and got kind of red. I had him outline the redness to monitor the swelling. It took a while for it to go down but it did not get worse. The gear is fine is clean and he is fine now.
If you actually have a sore seek medical attention right away last think you want to do is take the wrong antibiotic and you may even have a staph infection.