How can the white raised ulcer in gums be cured?

Hi,

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This is not an ulcer, infact it is big pus boil that has occurred due to some infection in your underlying tooth. You should start with an antibiotic regime immediately and get it treated. Most probably root canal treatment and scaling will be done of teeth under question. If it is not paining that does not mean it will remain silent for long. It can trigger up anytime. You must see the dentist as soon as possible. If you get a late appointment then I can prescribe medicine for you. Give me followup after a day for it.