Please get that PET scan. Don't ever just wait and watch. Melanoma can spread to vital organs overnight. My sister had a small spot removed 11 years ago, continued each year to get blood work and chest x-ray, each time getting an all-clear. All of a sudden she has metastatic melanoma in five lymph nodes. She has gotten treatment at M D Anderson in Houston and is doing very well. They saved her life. A PET scan is how they found the five melanoma nodes.
Also, I think you should see an oncologist and not just a regular GP.
I hope all goes good for you.
Carolyn from Tennessee