Cat Scratch Disease: This is a common condition in children, caused by Bartonella henselae, typically presenting with a painful lymph node near the site of a cat scratch. The age of the patient and the description of the lymph node make this a plausible diagnosis.

Infectious Lymphadenitis: Bacterial or viral infections can cause lymphadenitis, which presents as a painful lymph node. Common pathogens include Staphylococcus aureus, Streptococcus pyogenes, and viral infections like influenza or adenovirus.
Tuberculosis: Although less common in some regions, tuberculosis (TB) can cause lymphadenitis, especially in children exposed to TB or in areas with high TB prevalence.
Atypical Mycobacterial Infection: Similar to TB, atypical mycobacteria can cause lymphadenitis, particularly in immunocompetent children.

Lymphoma: Although rare, lymphoma is a critical diagnosis not to miss. It can present with lymphadenopathy, and a painful lymph node, especially if it's enlarging or persistent, warrants further investigation.
Neuroblastoma: This is a type of cancer that can present with lymphadenopathy, among other symptoms. It's more common in younger children and can be life-threatening if not diagnosed early.
Histiocytosis: Langerhans cell histiocytosis can cause lymphadenopathy, bone lesions, and other systemic symptoms. It's rare but important to consider due to its potential severity.

Kikuchi-Fujimoto Disease: A rare, self-limiting condition that causes lymphadenitis, more commonly seen in Asian populations and typically in older children or young adults.
Kimura Disease: Another rare condition that presents with lymphadenopathy and eosinophilia, more common in Asian males.
Castleman Disease: A rare disorder that can cause lymphadenopathy, among other symptoms, due to overgrowth of cells in the lymph node.