Highly doubtful this is a hernia, particularly in light of your history. Lancing an abscess would not make it worse. At the least, it would not help (if done too soon, before it was "ripe"), but it would not make it worse. The problem with waiting for it to "explode" is that there can be damage to surrounding tissue while it makes its way to the surface, but even that is not the end of the world, since it essentially does the same thing as incision and drainage.
The Flagyl may help (it is a broad spectrum antibiotic), but it will not cure an abscess at this stage. It can help keep it from expanding or entering the bloodstream.
Bottom line, I would not wait three weeks to address this. See someone local, but also notify Dr. Remzi about what is going on.
While you wait for treatment, put hot, moist soaks on it for 10-15 minutes, 4-6 times a day.
Good luck!
Jan
