A vet. I noticed mouth rot in my baby male and was hoping it would go away on its own, but it just kept getting worse. I believe there are a few things you can do to rinse the mouth out and swab the infection but anti-biotics via injection worked within one week for me. Hope all goes well for you, my full vet bill was $90 and well worth it.

There are often underlying causes to mouth rot which is another reason a vet is your best option.