What are these small lumps behind my ear and nape/neck areas, its also painful.i just had after after my hair color though its not my first time?

Lymph node: There are thousands of lymph node located around the body that help screen out germs in the serum before it returns to the circulation. There are many in the neck, head and behind the ear. At rest these are often 1/4 inch in diameter and may grow to marble sized when reacting to a stimulus. Bug bites, or skin irritation can increase their size.They should shrink down to nl size over a few wks.