Poor guy. If he has canker, that can be treated with metronidazole which you can find online. If you have a trusted vet you may be able to get him seen, and get a diagnosis. Here is where to get metronidazole, but a vet may be quicker:
https://jedds.com/products/metronid...YY_2Zj5TCHVTl5dhvJ45nol5HQS7pfw1RkN8y-0-5VF05
Dosage is 250 mg daily for 5 days.
https://jedds.com/products/metronid...YY_2Zj5TCHVTl5dhvJ45nol5HQS7pfw1RkN8y-0-5VF05
Dosage is 250 mg daily for 5 days.