Persistent visible painless lymph nodes in a four year old three months after a viral infection?

Common issue: Lymph nodes are located throughout the body & generally noticable in exposed areas like the neck. They are usually pea sized at rest and enlarged when stimulated by bug bites, dermatitis, drainage or infection. They rarely can become damaged by infection & grow to golf ball size & need drainage or removal. Most enlarge and later shrink back down within a 3 wk cycle unless chronically stimulated.