i have had pain like that and it was due to my billfold in my back pocket. since i quit wearing it that way, i have not had it any more. when i have returned to wearing it that way, the pain has returned - quickly when i did it soon after stopping, and not so quickly the longer i kept it out of my pocket. these days, i can wear it for days and never tell it. i wont ever wear it there full time again. posture is another problem effecting this. in fact, anything one does on a daily basis will have an effect. look at someone who crosses their leg in a certain spot habitually. they will have spider veins there. when i would drive the same car all the time and my knee would rest on a certain point, it would start to get tender and i would have to adjust to another position.
i liken it to the same problems as carpal tunnel and bed sores. the nerve is irritated in the same way every day and the protection from this irritation wears down. it becomes more and more sensitive over time. i do believe it is repeated pressure on a specific place that causes this. nerve pain takes a long time to heal, and that is after the stimulus for it has been removed.