If it does get to the point where one or both break on their own soon, I'd try to get all the pus out I could (it will be the consistency of cottage cheese) and keep the wound open to let it drain. Keep the wounds super clean to prevent bacteria from causing infection.
Do you have any zoos or similar animal attractions anywhere near you? How about a university that has a veterinary program? If you can't find a vet that treats turtles, I'd ask a regular vet---this is not an operation per se, but a careful cut with a sterilized instrument.
I can't tell you what to do, but you might want to look at this link:
http://www.chelonia.org/Articles/Terrap ... ection.htm This shows the procedure that a herp vet would use to remove an abcess. Perhaps you could show it to a regular vet to give an idea of what's involved (but I would think a regular vet would know this). Please note that the box turtle in this pic has been anesthetized, which not all turtles are. There may be an issue with holding the head steady to make the cut.
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-