Benign Prostatic Hyperplasia (BPH): The patient's symptoms of urinary hesitancy, decreased force of urinary stream, post-void dribbling, and nocturia are classic for BPH, especially in an elderly male. The presence of a firm, hard nodule on the left lateral lobe of the prostate further supports this diagnosis, although it warrants further investigation to rule out malignancy.

Prostate Cancer: The firm, hard nodule found on the prostate requires further evaluation, such as a biopsy, to determine if it is malignant. Prostate cancer can present with similar urinary symptoms to BPH and is a significant concern in older males.
Constipation: The patient's last bowel movement was 7 days ago, which could contribute to the urinary symptoms due to the proximity of the rectum to the prostate and bladder. Constipation can cause urinary retention and other lower urinary tract symptoms.
Urinary Tract Infection (UTI): Although not directly indicated by the symptoms provided, UTIs can cause urinary frequency, urgency, and discomfort, which might overlap with some of the patient's symptoms. The presence of abdominal pain could be related to a UTI, especially if it involves the kidneys (pyelonephritis).

Prostate Abscess: Although less common, a prostate abscess could present with severe pain, urinary retention, and systemic symptoms like fever. It's a serious condition that requires prompt diagnosis and treatment.
Kidney Stones: The left lower quadrant abdominal pain could be indicative of a kidney stone, especially if it radiates to the groin. Kidney stones can cause severe pain and urinary symptoms.
Diverticulitis: Given the location of the abdominal pain (left lower quadrant), diverticulitis should be considered, especially in an elderly patient. It can cause significant pain, changes in bowel habits, and potentially lead to more severe complications like abscesses or perforation.

Prostatic Infarction: This condition involves the sudden loss of blood flow to the prostate, which can cause acute pain and urinary symptoms. It's less common but should be considered in the differential diagnosis of acute prostate-related pain.
Bladder Cancer: Although less likely than prostate cancer, bladder cancer can cause similar urinary symptoms, including nocturia and changes in urinary stream. It's more commonly associated with hematuria (blood in the urine), which is not mentioned in the scenario.