3 wks post TT my belly button split and it has a quarter size hole. What should I be doing to take care of it?

Thank you for sharing your question and photograph.  The best treatment is to keep the area clean and  covered with a thick emollient like Aquaphor and a non-adherent gauze.  This will allow for your body to slowly heal itself from the inside-out.  I would maintain close contact with your surgeon to ensure no further healing issues. 

It is best to follow your physicians' instructions. If you are unhappy with their recommended treatment protocol then it is best to discuss it directly with them.