I can see that you are suffering from post-appendectomy
pain and it can be a very annoying symptom sometimes.
During appendectomy, many nerves are cut and following surgery because of this one can feel pain and tingling
(pin like sensation) over the area of the scar. This feeling can persist upto 1-2 years after surgery and it gradually dies down.
In your case, you have been extensively investigated and things seem to be normal. Just give some time for this pain and stiffness
to go away. I suffered from a similar problem after my appendectomy.
You can carry out some relaxation exercises to take your mind away from the pain.
Hope you get well soon.