Girls, hello. The newborn daughter seems to have stomatitis. She has a…

Girls, hello. The newborn daughter seems to have stomatitis. She has a sore spot under her tongue. I see only one so far. What should I do? Tomorrow is the weekend. I'll write to the pediatrician in the morning. But what can I do now? The baby is sad and worried. How is it usually treated? And how long does it take to heal?