Are you addressing thing up and down stream of the hip?
You see it at the hip, however, it may originate somewhere else.
Maybe you hit the tolerance for 4 reps at that weight yet in relation to your healing?
Sometimes as things are healing something may come up when you least expect it.
A weight or skill which was fine before may not be ok at another point during the healing then is fine again.
May be something you want to get checked out to see exactly what is going on with it.