Axolotl mouth sore/growth. Advice, please

[SAS]

My job includes caring for an axolotl along with other amphibians and reptiles. I believe it is a male. About 2 months ago he developed a pinkish sore/growth on/in the left side of his mouth. It doesn't appear to have grown beyond what is in the pictures and hasn't lost any weight. Other than that, he seems fine and eats well. I'd like to find out what it is and if I should take any action. Help would be most appreciated .

 

[Styx&Ling]

My friends axolotl had something like this awhile ago, the lotl bit a plant and then it's mouth ended up growing a sore, watch the red spot for a few weeks and see if it grows or shrinks.

 

[SAS]

My friends axolotl had something like this awhile ago, the lotl bit a plant and then it's mouth ended up growing a sore, watch the red spot for a few weeks and see if it grows or shrinks.

Many thanks. There is a plant which I will now remove.