Can anyone specify what it might be?

Unfortunately, the symptoms and photo described by you are not enough to make an accurate diagnosis, because they can be caused by many different causes. One possible reason could be an allergy or sensitivity to some food or cosmetics (e.g. toothpaste). Other possible causes include gastrointestinal infections, anemia, diabetes, weakened immunity, smoking, and even stress. The pharmacist, within his competence, may propose over-the-counter products: Dentosept A - a liquid used in inflammation of the oral cavity and gums, in aphthous ulcers and as an auxiliary in periodontitis. In the composition of the preparation there is also benzocaine, which provokes local anesthesia. https://www.gdziepolek.pl/produkty/21852/dentosept-a-plyn-plyn/apteki?pvid=35712#internetowe Dezaftan MED spray - an oral aerosol with antibacterial and local anesthetic effect. https://www.gdziepolek.pl/produkty/100635/dezaftan-med-oraseptan-aerozol/apteki?pvid=249832#internetowe Eludril Classic - a remedy that relieves inflammation of the gums. The ingredients of the preparation are responsible for antiseptic properties, have antifungal, soothing and analgesic properties. https://www.gdziepolek.pl/produkty/95186/eludril-classic-plyn/apteki?pvid=235672#internetowe If symptoms persist and are bothersome, it is best to consult a doctor or dentist who will be able to carefully examine the tongue and perform appropriate diagnostic tests if necessary. Based on the results of the tests, the doctor will be able to make an accurate diagnosis and prescribe appropriate treatment. If you are unable to get to your primary care doctor, the GdziePoLek.pl service also allows you to obtain a teleconsultation with a doctor: https://www.gdziepolek.pl/telekonsultacja The action and composition of individual drugs can be checked by clicking on the attached links on the gdziepolek.pl website, which also allows you to book them at the nearest pharmacy.