It looks like oral thrush. Thrush appears as white
patches in the mouth. Usually they can be seen on
, inside the cheeks, on the inside of lips, under the tongue, and in the back of the throat. I suggest you to get an examination done from your doctor and get a KOH examination of the scrapings done of these white coatings.
Nystatin (Mycostatin) liquid is used by swishing a bit in your mouth several times a day and then swallowing the medicine.