If local anaesthetic was administered, you may feel numbness for 1 to 2 hours after the procedure. It is advised to only start eating after the numbness has subsided to prevent biting your cheek by accident.
Also, note that it is normal to experience some soreness and sensitivity for up to 2 weeks after the procedure. Some other tips to note:
Chew gently and slowly
Chew on the opposite side of where the filling was done, if possible
Avoid hot, cold, sweet and sticky food and beverages