I am a pediatric dentist and he should see a dentist right away. The swelling is a sign of an infection. If there is still a flap of gum tissue covering the back part of the molar then food is getting stuck underneath there and not getting cleaned out leading to an infection. It is not normal for his face to be as swollen as you mentioned. He needs to be put on antibiotics right away. This is not just normal teething. Please call your dentist back and insist he is seen. Good luck. You can contact me directly if you would like ____@____.com.