I REALLY REALLY appreciate your response I was so worried I am glad that it isn't anything that I can't helpTympanic abscesses have to be lanced. What you see is only half of the problem. The other half is inhibiting his swallowing. Anyone can lance it, I do it all the time. But your first time should be done by a vet so you can watch and learn.
Your turtle's abscess isn't ready yet to be lanced. They need to be ripe or they'll keep coming back. You'll know when it's ready. It will be a lot bigger than it is now.
I use a new single edge razor blade. Wash the blade and the abscess site off with Betadine then make an 'X' cut across the middle of the abscess, top to bottom. The 'X' makes it easier to express the contents of the abscess. You don't really have to squeeze it, once you've cut the skin it pops right out. Then I take the blunt end of a tooth pick and pick out the rest of the pus particles. Flush it with more Betadine in a syringe with a bit of force. If you don't get all the pus out it will come back. It will start to heal in a couple days, but you need to keep the turtle indoors for about 2 weeks to be sure flies can't lay eggs on the site. A regimen of antibiotics is called for.