What Causes Redness And Soreness At The Back Of The Ear After Ear Piercing?

i recently got my earlobes pierced for the second time and they are NOT red, swollen or sore but it is red and sore behind my left ear. there is no visible lump but it is tender to the touch. i do not have a fever nor do i have the symptoms of an ear infection. what could this be and what should i do?