Good day and thanks for your question. You are likely to have a Canker sore. Please do not pop it, it ll go by itself without treatment in a week or two. But you said its big and its hard for you to eat, then use Benzydamine hydrochloride mouthwash or spray for pain, Hydrocortisone sodium succinate cream to reduce inflammation then practice good oral hygiene, avoid foods that irritates the mouth such as citrus fruit, acidic vegetables and spicy foods. If these interventions are not helpful, please kindly consult a dentist. Hope it helps. Thank you.