“What is the cause of my hip pain?”

For 1 year? Then absolutely. AVN, Labral tear, etc., are concerning.

At one month I would see my primary care physician if the pain is getting worse. If the pain is improving I would just be patient.

If you develop this pain doing walking or simple exercise, yes, you should see a doctor. If this comes out during vigorous exercise, I would not be as concerned. Certainly you could have strain of hip internal and external rotators. It is very doubtful that you do have arthritis and it is very doubtful that you had a congenital disease that caused a change in the mechanics of your hip.
I hope this helps you.

Dr. Palmer