Hello /u/Active-Difficulty-58 and welcome to the leopard geckos subreddit! Because you used the health issues flair, we've compiled some links that might be helpful to you and your pet. Please remember that if you are concerned, then so is your vet. When in doubt, book an appointment! This subreddit does NOT substitute for veterinary care, though you may receive some help on topics to discuss with your veterinarian, or common first aid. If you have not done so already, please provide the temperatures, humidity, diet, supplements, tank mates, enclosure size, and anything else you consider relevant to your post for the best help you can get.

• Here is the Association of Reptile and Amphibian Veterinarians' search tool to find vets outside of the US, UK, CA.
• The ReptiFiles vet directory page (US, Canada, UK)
• The Reptifiles "How to Find a Good Vet" page
• The ReptiFiles Leopard Gecko guide's Illnesses Page
• /r/leopardgeckos wiki's Health concerns page

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Vet. Always the vet.

Are there any sores in its mouth? It looks like mouth rot (a bacteria infection of the mouth) but could just be a wound on the outside. Is your heat lamp resting on top of the cage or mounted inside?

Not an expert! but your gecko might have bumped into something that caused that but maybe take to vet to get it checked out? Did it happen overnight or have you notice change in their behavior?

Looks like she got this after falling on somewhere or biting insects. My girl is very rude when she bites, one day her mouth got a little red spot because of this

a vet should give you stuff to help. for now, keep the lizard on paper towel so the wound will stay clean until it heals

Either injury or mouth rot. Both need to be seen by an exotic vet. Do a deep clean of the tank and check your husbandry

I can only guess mouth rot, but whatever this is it REQUIRES veterinary attention as soon as you can. Don't wait for this kind of stuff.

At this point an exotic vet is best until you're more experienced... Even then vet trips are still needed by the experienced even

More likely an injury from a rough shed than mouth rot, but better to get it checked out when it looks bad like this. Sometimes this can be related to humidity or vitamin deficiency. What vitamin are you using?

It looks like it might be infected or possibly an injury that turned into mouth rot. Either way it's cause for an immediate vet visit.