Why is There Discharge/puss Coming out of my Belly Button? (photo)

It looks as though there has been some compromised to the skin from the inferior border of the navel down. This would explain the drainage which should be able to be managed by cleaning the one periodically.

Appears as fat necrosis issue. Always best o see your surgeon for treatment in person. This can be addressed by an office visits. 

It is hard to make a diagnosis here without an exam, but some form of infection or  "fat necrosis" is likely. You should make an appointment for an office visit with your surgeon for instructions.

All the best.