Hi, welcome to the forum, the commonest cause of such growth can be secondary to sore throat
(streptococcal and others), Vitamin B-complex deficiency, reflux pharyngitis, leukoplakia..
If there is a infection, you need empirical treatment with a course of broad spectrum antibiotic against prescription. Send blood or throat swab for culture and antibiotic sensitivity. Need to do antiseptic mouth gargle to take care of source of infection.