Musculoskeletal Strain: The patient's symptoms of right-sided back pain, tight feeling near the hip, and pain exacerbated by lifting the leg, along with the history of lifting heavy objects at work, strongly suggest a musculoskeletal strain. The pain level and the fact that it's slightly improving also align with this diagnosis.

Lumbar Disc Herniation: The pain radiating to the hip area and difficulty lifting the leg could indicate a lumbar disc herniation, especially if the pain is radicular (radiating down the leg). The lack of significant relief with NSAIDs and acetaminophen does not rule out this condition.
Lumbar Facet Joint Pain: Pain that is exacerbated by movement and improves slightly with rest could be indicative of lumbar facet joint pain. The location of the pain near the hip and above could involve the facet joints.
Piriformis Syndrome: This condition, where the piriformis muscle irritates the sciatic nerve, could explain the pain in the hip area and difficulty lifting the leg without pain.

Kidney Stone: Although less likely given the description of the pain and its relation to lifting, kidney stones can cause severe back pain that radiates to the groin area. The absence of other typical symptoms like nausea, vomiting, or hematuria does not entirely rule out this diagnosis.
Spinal Infection (e.g., Osteomyelitis, Discitis): Infections of the spine are rare but can present with back pain and require immediate medical attention. Risk factors such as recent travel, immunocompromised state, or intravenous drug use would increase the likelihood.
Cauda Equina Syndrome: A medical emergency characterized by low back pain, bilateral sciatica, and signs of nerve root compression (e.g., urinary retention, fecal incontinence). Although the patient's symptoms do not fully align, any suspicion of cauda equina syndrome warrants urgent evaluation.

Osteoid Osteoma: A benign bone tumor that can cause nocturnal pain relieved by NSAIDs. The patient's pain waking them at night could suggest this, although the lack of relief with NSAIDs makes it less likely.
Spinal Tumor: Both primary and metastatic spinal tumors can cause back pain, often worse at night. The gradual onset and nature of the pain, along with the absence of systemic symptoms (e.g., weight loss, fever), make this less likely but not impossible.