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.
At this point of time we cannot say for sure without medical finding. For above symptoms consult ENT specialist. Take care and regards.