Mouth ulcers on the inner lips and under the tongue are usually painful but commonly improve within 1-2 weeks with proper care. They can occur due to stress, lack of sleep, spicy foods, acidity, accidental biting, vitamin deficiencies, dehydration, or irritation from sharp teeth or braces. To get relief, avoid spicy, sour, very hot, or hard foods, as these may increase pain and irritation. Drink plenty of water and maintain good oral hygiene using a soft toothbrush. Gargling with warm salt water 2-3 times a day may help reduce discomfort and keep the mouth clean. Applying ulcer gels may help reduce pain and support healing. Vitamin supplements like Becosules may also help if the ulcers are related to a vitamin deficiency. Try to get adequate rest and reduce stress, as recurrent ulcers are often linked to stress and fatigue. However, if the ulcers are very large, keep returning frequently, last for more than 2 weeks, cause difficulty in eating or swallowing, or are associated with fever, weight loss, or swelling, you should consult a doctor or dentist for proper evaluation and treatment.