It's a long shot, but my best friend for many many years had the same problem as you WITH EXTREME PAIN in the same area.

The doctor had no idea what caused it.

We had been cutting trees a month earlier at his cabin and I suggested to check for Lyme Disease (Boreliosis)

His Doctor said none of the symptoms match Lyme but my friend insisted on being tested.

As soon as the test results came back, the doctor called: YOU TESTED
POSITIVE,
I have never seen anything like it.

He was treated for Lyme which was not easy.

But that's another story.

If you live in a concrete city or part of the world where lyme is not present, it's unlikely that you need to be checked for Lyme.