Thanks for the query.
It probably might be an enlarged lymph node
. Lymph nodes get enlarged when there is an infection. Since it was in the recent past you had got your ear lobe pierced, it might have caused some infection. You may require some antibiotics since it is inflamed (painful to touch and reddish in colour). Please visit your physician to get it examined and treated.
Hope I have answered your query. Let me know if I can assist your further.