What could be causing pain in right hip?

I’m a new cyclist in my 40s, used rental bikes for the past year before buying a second hand drop bar bike with flat pedals 4 months ago. I’ve been riding it about 3 times a week since and have slowly built up the mileage (longest ride so far was a slow 90km).

Recently I’ve developed soreness in my right hip. I don’t feel pain while on the bike and only noticed something was wrong at night when I rolled over from my left side to my right in bed. At first I hoped it was just part of the usual aches and pains and I ignored it for a bit but of course it just got worse after every ride. I took a week off the bike and it improved a lot, but after short 30km ride it was very sore again.

The pain feels like it is in the hip socket or the tissue immediately surrounding it. It’s not a sharp pain, but is very sore, something similar to the pain you might feel when over enthusiastically massaging a tight spot in your hamstring. The pain usually only manifests itself in quite specific situations, for example when I internally rotate my hip, especially at the end of range of motion:

or when I roll over from my left side to my right with bent knees:

Otherwise I don’t usually notice it. Strangely I don’t really notice it when on the bicycle either, however if I keep on cycling, the pain gets worse and starts to ache constantly. At its worst it keeps me up at night and is stopping me from going on any decent bike rides.

I have a feeling it might be something to do with going up hills, especially in a lower gear out of the saddle, something which I’ve only recently started to do.

I had a go at diagnosing from cycling articles, the closest I found was piriformis syndrome, but that doesn’t seem to quite match and annoyingly most of the exercises they recommend for that I seem to have been doing anyway.

It’s a very localised pain, so I’m hopeful there is a simple cause, does anyone have any idea what it might be and how I can fix it?

Thanks!