22 yr old waitress. suffering from severe hip pain of inner hip joint. worse after i've stood on my feet for 3+ hours at a time. causes/relief?

Sacroiliac joint : If this pain is posterior in nature, you may have sacroiliac dysfunction/sacroilitis secondary to either leg length discrepancy from carrying trays with hips tilted. Have your leg lengths checked and use a heel lift/orthotic for correction to see if your pain improves.

Anterior hip pain: May be developmental hip architectural issues. Get x-ray & orthopedic exam. Sprain, strain, referred lumbar radicular pain, pelvic referred pain, hernia, etc. Should be considered. Arthritis less likely, given your age.