(nerve?) pain in extraction site

Hi, i am having 24 and having extractions of 4 molars so i can have braces on.  Have had 2 removed so far, first was a lower and ended up with a dry socket_agony!..Had the second (upper) extracted nearly 3 weeks ago now, have not had too many problems but i do experience extreme sensitivity in the wound area and the adjacent tooth when having cold drinks...also when i use a small syringe to slean the site with salt water and there is a particular part which causes excruciating pain which is similar to the sensitivity but MUCH worse!It feels almost as if in that section the nerves are exposed or something!Do i need to do anything about this or will it just go away?
Any help would be much appreciated