Many possibilities. Could be tonsillar calculi (stones in your tonsils), strep or other bacterial infection causing exudate, or thrush (oral candidiasis). Something like that requires examination to know what it is.
Tonsil stones. It is possible that you have tonsil stones (tonsilloliths) in your tonsils. Your tonsils may have pits (crypts) and food can accumulate here. Over time this can lead to a localized infection of your tonsils leading to a sore throat. This can be managed with salt water rinses after each meal, using a water pick on the tonsils, or manually removing the stone. Tonsillectomy is the final option.