Most probably its food debris... when you sleep at night dont forget to brush and start using a mouthwash for 15 days. Develop a habit of flossing also if you dont do it yet. If the problem persists after a week then see a dentist. Nothing to be worried about.

Hello These particles may be either food debris or tonsil stones. This is more common in people with tonsillitis ( inflammation of tonsil ). You can avoid it by brushing twice a day ( especially during night as the saliva flow is less during night, hence causing more accumulation of debris) & by doing warm saline rinses ( add a pinch of salt in Luke warm water). Also get your tonsils checked. Wishing you a speedy recovery. Regards Dr Surabhi