Hi.. Thanks for the query.. As per your complain a small white patch or sore inside mouth that does not go away for 4 months is a sign of concern as it can be related to some malignant tranformations.. You should consult an Oral Surgeon and get evaluated and a thorough clinical evaluation and investigations like Biopsy can be done for diagnosis and then only an appropriate treatment can be done.. As of now you should avoid biting it off as it can become painful and inflamed and further worsen.. Take a soft diet and avoid eating hard and sharp foods to prevent its irritation.. Hope this helps.. Regards.