it's the scar from the piercing,it's normal..it'll go down once everything is healed I promise.
its a polyp/keloid,I had the same thing about 3 months after I had mine done. I went to my piercer and they said just do sea salt soaks a lot. eventually it went away but took a few months. at the time they told me give it a few weeks if no improvement they would have had 2 remove the post and cut off the lump and wait for it to heal and there was no guarantee if the hole would still be open.does Claire's do lip piercing?
its probably a keloid
they can take a few months to heal so if it is you just have to leave it and wait
but you should also ask your piercer