Boy, do I know what you are talking about. I recently had a hen that had the identical problem.
She had apparently got something stuck in her mouth, and caused an absess in the bottom left corner of her mouth, same as yours just on bottom. This caused swelling in the area, between her eye and nostril, and even a bit on other side of face. No respiratory problems either. I put her on antibiotics for 2 weeks, no improvement. I then noticed the absess. We cleaned it out, and it appeared to be like woodshavings. the hole continued to get stuff lodged into it, and were not able to remove it the second time. We took her to the vet.
The bad news is that they had to put her under, clean out the absess, which was connected to the above area through sinus passages and also caused a respiratory infection. Lancing on our own did no good as it was below the surface. So they cleaned it out, and lanced her face, removing pus in the sinus cavity and a cottage cheesy substance in the absess. Cost? $245.00...
She has been on Baytril for a week and a pennicylin med and pain med for 2 weeks. I had to flush the face opening once per day. She has a return appointment on the 4th, and the swelling is still in her face, but the mouth wound is closed now. I am sure they will have to re lance the sinus cavity to clean it out again. They had me flush with a very WEAK solution of betadine and warm water in the opening, and flush her nostrils out with it also, holding her upside down so it didnt go into her lungs.My suggestion ultimately is to get her to an avian vet to look at it as mine would not have improved at all without it. Granted, she isnt better yet, but, she will be probably after another lancing session and another $200.00 darn.....there goes my computer upgrade I wanted.... frown
Cara Smith