The area around the watch definitely did not tan. The skin under the watch just turned white.
Hello,
The area around the watch might have tanned which has given the appearance of white discoloration where the watch is. Do not wear watch for some time and the area should blend with the surrounding skin after exposure to sun. If the symptoms persist the get it examined from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.