Hi.. Can understand your concern.. Swelling under the extraction site can occur due to any of the following reasons.. -It may be due to excessive trauma caused during extraction. -It may also be due to root piece left out in the socket and thus persistant source of infection is present.. -If the tooth was already infected and proper cleaning or curetting of socket is not done and a focus of infection is present into the socket. Better for you will be to revert back to your dentist for evaluation of exact cause of swelling by getting an IOPAR ( X-RAY ) done to let him or her know the exact reason for ur discomfort and can advise you proper medicines. The other complain of your about pain from back part of ur jaw and difficulty in opening the mouth may be due to your third molar ( wisdom tooth) if it is erupting or impacted or the gums over the tooth may be getting inflammed.. Or if any other tooth in that region is infected and causing pain and swelling. These may be in general few frequent causes of your problem. See your dentist soon. Proper antibiotics,painkillers (which suits you and does not cause all ergy) and mouth opening exercises can very well solve your problem. Dont get panic. You can very well get relieved of your discomfort. But see your dentist soon. Thanks and regards.. Dr.Honey Nandwani Arora.