I think the area didnot heal the way it should and the space closure never occured .Now ur experiencing these symptoms as the food might have started accumulating in that hole and u have now developed infection because of which there is fever and swelling.First of all gently and very carefuly trp to clean that area and hole and remove all the food particles and the debris present there with the help of soft brush and a cotton piece.You can also irri9gate that area with a mouth wash as it has antiseptic properties.Start using warm saline rinses as they will relieve pain and selling and promotes healing.Do visit ur dentist and get clinical check up and Xray done for correct diagnosis of the condition and treatment accordingly.There can be a bone or tooth piece left behind that didnot allow the conplete healing to take place.................for more info refer the link.................................