Not proposing an explanation or remedy, just to mention a palliative of pain/ache:
After having my soothing cleansing hot shower, I now aim COLD water from the shower-head at my leg/groin. This seems to persuade nature to cool it and my ache signals become muffled or less noticeable -- at least for a period of time.
I surmise that pain and pleasure signals are to some extent subjective -- if the body and mind are persuaded or cajoled into believing that an upswing or downswing is in progress, that interpretation will be accentuated.
If cold water spray or immersion helps, well cold water unlike painkiller pills will never become addictive.