Why does your tragus piercing have a big bubble?

Keloid scar or hypertrophic scarring. Hypertrophic scarring is common with cartilage piercings. Go out and buy some Tea Tree Oil. You can find it at target or Walmart by the vitamins and I'm sure any drugstore would have it. After you clean your piercing, use a q-tip and dab a bit of the oil on the bubble then leave it on there until you clean it that night. Don't put it in the actual piercing. If its new, wait till its at least a month old to use the oil. Apply the oil once every day and every other day if it gets drying. The oil dries up the bubble and it'll flake off in layers until completely gone. Good luck :)