It might be a condition of an impacted teeth characterized by pericoronitis (inflammation of the gum flap) in these conditions there will be gap between the teeth as well as a gum flap. Food lodgement is common resulting in infection with symptoms of pain and swelling .
Next Steps
Visit a dentist. Get a full mouth x-ray done / to decide / further treatment.
Health Tips
Use a mouth wash regularly/ Swiss ur mouth after every food intake .