But your insurance will find out. This can prevent you from being eligible for life insurance as well. Not a smart move IMO.
+1 he may not go tell your family or friends, but he WILL write it down in your file unless you have a cool doctor, and those records will follow you. I doubt very seriously that the doctor is going to run a hormone panel for an infection and if all other lipids, liver values etc are in the normal range and being monitored regularly from the patient the doctor may suspect gear use by looking at the individual but nothing will be confirmed. B12 shot, bug bite etc. all they need to know is you have an infection from something. You wont know what type of infection anyways so more information generally wont help that much anyways. Good luck, but since the redness is gone and the swelling is going down I'd say you probably got through the worst of it, I would avoid that site for at least 2 more weeks and let it heal completely.
If you it persists for any longer it might be a good idea to still go in to an urgent care or something just to have it looked at. Costs less then 100 bucks generally even without insurance and they can still prescribe something broad spectrum just in case.