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Hello. Thanks for the question.
The main worry I have when there is a lesion on the mouth, is a uremic ulcer. These occur secondary to kidney disease or kidney failure. The other big rule out, would be a tooth infection or dental disease. They can both cause bleeding ulcers in the mouth and around the mouth. Tooth root abscesses can rupture out through the skin.
I would have a good oral exam done and also check some bloodwork to look at the kidney enzymes. If the kidney enzymes are normal- great. If high, then we need to figure out if it's a kidney infection (curable) vs kidney failure (manageable but not curable). If there is dental disease, then anesthesia and removing any infected teeth is curative. If both of those are normal, then it could just be a skin infection that is treated with antibiotics and topical therapy.
I hope this helps, let me know if you have any other questions.
I would put dental disease up there as the number one rule out. If that is normal, then I would think some type of skin infection. It's not quite in the area I would expect with kidney disease.