What is this bump on my industrial piercing and how can I treat it? (Photo)

The photo suggests that this is a small keloid. Especially your history of the scar tissue expanding over time is highly suggestive of a keloid. To be sure have it checked out by a plastic surgeon or dermatologist. In many cases, injections can significantly reduce the scar tissue but if that is inadequate a small surgical procedure is often effective to remove the keloid. I hope this information is helpful for you.Stephen Weber MD, FACSDenver Facial Plastic Surgeon

Although an examination is required to make a definitive diagnosis, the photo and history are suggestive of a small keloid.  This isn't an unusual occurrence with such piercings and could potentially become worse with reinsertion of the piercing.  Treatment for such scars is generally a combination of steroid injections and surgical removal.

You will likely need surgical removal of the overgrown scar (keloid) and cartilage, and subsequent series of steroid injections to keep it calm and minimize recurrence.  And don't re-pierce it.