When I had an abscess I was told that it was necessary to take antibiotics for a week (in my case) before he could continue with treatment, otherwise there was too much risk of infection spreading. However unpleasant it seemed to make sense.

I flew twice during that week and don't recall the flight making it painful in itself, but it was painful anyway. I ended up going to a chemist for painkillers, they gave me strong NSAIDs of some sort which worked.

Neil