Hello metoo,
What you are describing sounds exactly like something that I and others have run across. For me, it was a major issue for the first few weeks, and then would pop up periodically for the first year or so. Here is my amateur understanding of it from talking to my doctor and others.
That bump you are describing is in fact the greater trochanter. There is a bursa (small fluid filled sack that acts as a cushion where muscles or tendons rub across bones) that sits on the outside of the greater trochanter. When this gets inflamed, we have trochanteric bursitis. My doc prescribed gentle repetitive exercises. If that did not work, a cortisone injection into the bursa is sometimes done to knock out the inflammation.
For me, the real key was figuring out that the IT band runs across that bursa, and that is what was causing the bursa to become inflamed. Stretching out the IT band on a foam roller so that it has less tension across the bursa has led to very good relief for myself and others. I think that what may have started it in my case, is that my leg came out about 4 millimeters longer, so this stretched the IT band extra tight, putting pressure on the bursa where it crossed the greater trochanter. There are many other causes of tight IT bands after this surgery, and trochanteric bursitis is often the symptom. It always seems to go away through either time, PT, foam rollers, or cortisone injections.