Why does my hip hurt?

It hurts because your core (abs, glutes, ad/abductors, etc) have weakened to the point where any underlying genetic hip disorders (however minor) will start to play a bigger part in hip rotations.

I broke my pelvis in a 5m fall a few years back (I'm 60) and the surgery required to fix it cut through my glutes. This resulted in a much weaker right glute and abductors. Until I implemented a regime of core-specific exercises combined with nightly glute stretching and twice weekly use of a roller on my lower back, my right glute would always seize up after a few months and I'd need to see a professional. I haven't had any problems in the last year and provided I maintain that core strength I do not anticipate any further problems.

I could quite simply be that you failed to get a hipgnosis.

https://browse.gallery/en/hipgnosis/