Would pinch nerve at l4-l5 cause hip pain/popping or would it be a pinch nerve at l5-s1? or can it be either?

Can be either: Development of leg pain may help distinguish between L5 or s1 radiculopathy. Sometimes it is very difficult to distinguish on clinical exam, and other testing may be required. You should be evaluated by your physician to help make the diagnosis.

See details: A pinched nerve in the lower back would not cause a popping in the hip joint. Have an orthopedist or rheumatologist check it out.