My brother says I should get treated because once in a while I get swollen lymph nodes? Is he right?

Depends where how. Swollen lymph nodes are common as a consequence of infections. Lymph tissue participates in the immune response against infection, so lymph nodes temporarily enlarge, then recede in size after the infection is conquered. Lymph nodes that enlarge beyond the size of a walnut, are very painful, or persist should be examined by your doctor.