Sir u need to show ua mouth ulcers on a thorough video consultation, and give detailed history, so I can diagnose and treat accordingly. As u have suffered from covid and is also diabetic, may be ua immunity is bit compromised. I suggest u to put stomacare on ua ulcers. Use H2O2 mouth wash 1tsf diluted in half glass of water three times. Take tablet Becosule once a day for 3 months. Keep ua blood
sugar strictly under control, follow up with ua endocrinologist/diabetologist