I'm new to this forum, but not new to amphibians, fish, and reptiles. Do you have a vet near you that deals with axolotls? If not, is there a reputable pet shop that has such knowledge? If so, ask the pet shop's owner what vet they use. If they cannot help you, try the zoo. This may sound strange, but they likely have staff with extensive knowledge of amphibians, and they would also have access to a vet who knows their stuff. Please do not seek medical advice on the Internet. You will find conflicting information and if you harm your pet, no one can be held accountable.
As for the tank mate, axolotls don't need tank mates, and it is generally best to keep them separate. Feeding accidents happen, where they snap at each other instead of their food. Also, each axolotl has his/her own unique personality. Some are just trouble makers and like to start fights. Safety is top priority, so while I will not give medical advice, I WILL strongly urge you to not put axolotls in the same tank. Experts will argue, but the undeniable fact is that an axolotl will not attack himself. Axolotls can be extremely vicious towards each other with no warning or provocation. You will avoid a whole slew of problems just by not housing them together.
Best of luck to you and your axolotl. May I ask his/her name?