Illness/Sickness: My axolotl has a bump on her side

Hello there!

I have returned after the weekend and just today I have noticed my axolotl A'den has a weird bump on her right side. It scared me, so I decided to ask for help.

She doesn't seem to be in pain or anything, she swims around and reacts to people and things around her, she is usually very active and this hasn't changed a bit, she eats normally (and she likes to eat a lot, I feed her by hand once every day or every other day with frozen mosquito larvae, sometimes she gets a bit of frozen fish fillet, but rarely), her tank is cleaned regularly, there is a small filter in the tank and the temperature isn't too high either. She currently lives in quite a small tank because I had to move and had to leave her old aquarium behind. It's now our third year of living together and I don't suppose she is much older than that

I thought maybe she hit herself, as I said earlier, she is very active and likes climbing up the flowerpots and rocks she has in her tank, but I'm no expert in axolotl keeping so I would like the opinion of someone with more experience. I am attaching some photos. Thanks for any help!

Is she swollen anywhere else near her rear end? I can't say for certain, but it looks like she's eaten something and it was either a little too much, a bit big, and is still working through her system- who was feeding her while you were away/when was she last fed? I've never heard of feeding mosquito larvae, as most people keep them on earthworms for the simplicity and completion of their diet primarily- it might be worth getting some earth worms to try her on, and watch for any poop and if the lump 'moves' or even temporarily disappears.

My concern with the lump if it doesn't go away is that it could be an infection caused by something she's eaten- but I think usually that comes with many other signs of lethargy, floating, etc. That, or she's eaten something that's having some trouble coming out. I'd check her bottom, as well as keeping a close eye on her for the next 24-48 hours, and if nothing has changed it might be time to put her in the fridge (which can apparently help them pass larger things as stones/gravel/etc.)

Hey there, thanks for the information you gave me. She was last fed on Friday morning, then we fed her on Sunday afternoon when we returned - I thought maybe she has swallowed a leaf from a plant she has there (she does that sometimes, but I never noticed anything bad happening to her).
As for the earthworms - you can't really get them here in shops and it's a little too cold for digging them out of the ground now. She seems to be doing well on these, I have fed her with the larvae most of her life and she was never sick or had any trouble.
Also today I have noticed the bump has shrunk to half it's size so hopefully it will all be fine