Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern. As per your complain and presentation of symptoms if you had sudden swelling over left side of face after tooth filling then there are a few possibilities: 1.If anaesthetic injection was given then there is a possibility that there have been an allergic reaction to the anaesthetic solution leading to swelling.. Other cause can be if the injection was given for upper back teeth then swelling can be due to Hematoma formation.. 2.Chances are rare but allergic reation to dental materials can also be a cause.. I would suggest you to consult your dentist and get evaluated a and if thete is allergic reaction anti-allergic medication like Cetrizine or Fexofenadine (allegra) will be advised.. For excessive swelling steroids can also be given.. Injectable steroids and anti-allergics are also advised in severe cases.. If it is Hematoma then alternate warm and cold compresses are to be done and the swelling will gradually subside.. If there is allergic reaction to dental material like filling material then removal of the material and replacing it with other materials followed by anti allergics with relieve.. Hope this information helps..