My daughter is 20 months. i noticed today that there is a small hard lump behind her right ear. it doesn't hurt when i touch it. should i be worried?

Exam: she must be examined to determine exactly what this growth is. Possibilities include: a cyst, abscess, infection,or skin tumor. Your question deserves pediatric evaluation.

Lymphadenopathy: I wouldn't be too worried. Likely a small lymph node, maybe a cyst. I would be more concerned if its getting bigger, or becoming painful/red/hot to the touch. If not getting better in a few weeks then get it checked out.

Node enlargement: occurs as a result of stimulation by the immune system, usually in response to a variety of infections. Enlarged lymph nodes behind the ears are usually caused by previous infection of the ear or scalp and are generally not significant health issues.

Lump: The lump represents a lymph node which may be the result of a respiratory illness or possible cradle cap.It is benign and will shrink over time