Cartilage ear piercing?

i got my cartilage pierced two weeks ago by my best friend and the piercing itself is completly fine and doesnt hurt or anything.. but i have like a bump not on my ear itself but like behind it on my head and its about a centermeter wide, it doesnt hurt or anything i just found it too.. its not too squishy sorta hard.. what could it be? i heard it may be excess puss that "dripped" down and like formed there.. is that true? and i have a freind who has the same thing but got hers perfessionally done.. WHAT IS IT? and is there anyway of getting rid of it? helppp