You need to observe symptoms...
I am not able to clearly find an association with mobile phones and wrist watch to this pain. Perhaps they may not be related.
Moreover I do not think of serious medical problems based on the history provided. You are requested to closely observe the symptoms. If the pain is troubling you significantly and if you have more symptoms arising from it, it entails a visit to your physician for detailed evaluation.
At this point, I don't think it is a sinister concern.
I will be glad to comment further if you can provide more information.