I would like to know if there's any filling present in teeth number 3?
Also want to know, if the pain still persists?
If yes, then there are chances of secondary caries.
If not, then as suggested by your dentist, use an interdental tooth brush to clean the area, as the gums and other surrounding vascular tissue areas do have healing properties.
Next Steps
Use an interdental tooth brush and mouth wash.
Health Tips
Don't use that region to eat anything hard, crispy or bony food items, brush gently and regularly.
it should heal very soon.