Thank you for the query. I would like to know your age and gender and whether you suffer from any comorbidities like diabetes mellitus. Sore tongue can occur due to number of reasons. Allergy to any food ingredient can cause it. Vitamin deficiency, is however the commonest cause, and you should immediately start on Vitamin B-complex supplements. You can apply commercial preparations in your mouth for symptomatic relief. Chlorhexidine mouth wash can help. Avoid hot and spicy food. Occasionally fungal infection may be a cause, in which case clotrimazole mouth paint application is advised. Apthous ulcer is another common cause for soreness in the mouth, specially in young adults. If the problem persists please do consult your doctor. Hope this helps.