Bubble-eye goldfish are a very delicate variety and it is essential to keep them in a tank with no protruding decor or that could damage the fish. Also avoid keeping them with skittish other fishes such as small orfe or even single tailed goldfish.
If the fish is in good quality water then the damage may heal over. Use TetraTest water testing kits to ensure the pH is between 6.5 and 8.0, (it should be the same pH in your tank as your tap water), also ensure the ammonia and nitrite levels are zero.
Feed the fish a quality food from the TetraFin range and perhaps dose the tank with some TetraMedica GeneralTonic to promote the healing response. You may also wish to dose the tank with 3 grams of table salt to every litre of tank water. Ensure the salt is fully dissolved before adding to the tank (salt crystals will burn the fish), and add at half dose on the first day, increase to full dose (3g/l) on day two of the treatment.
With good water quality, some TLC and a bit of luck the wound should soon heal over and the fish's fancy eye will be back to normal.