In order to achieve dislocation of the joint, the short external rotators have to be let down at their insertion point at the greater trochanter. When you do wall squats, that recruits a lot muscle fibers and puts a lot of stress on the still repairing rotator tendon. You can't do any damage, but it can hurt.
I overdid it a few times on my first surgery and that happened for me around the 10 week mark as well. I was feeling good and strong and did a pretty intense leg workout with just my body weight and a Bosu ball. I was hurting for a good week after.
Have you ever had a really bad ankle sprain? I did. A slight tweak would set it off for at least two years afterward. What happens to our hips in a BHR surgery is like an ankle sprain x10, so these occasional setbacks are to be expected.
I resolved my overdoing it troubles by using a mix of ice, heat, rest and massage. You'll feel better soon.