3year old child,swollen left occipital gland for 1year now,not painful, no other symptoms,swells with illness but returns to 1cm.what could be wrong?

Many possibilities : May be a reactive node secondary to viral illness vs blood disorder vs some underlying scalp disorder vs not a node but a cyst. Needs GP assessment and depending on the clinical assessment may need tests ordered to sort it out

Evaluation: He need to be evaluated by his doctor and have Pet CT and possible biopsy to find the cause so be treated.