How can I heal necrosis after my tummy tuck?

Necrosis from tummy tuck unfortunately can occur.  If this occurs there is usually  a time period allowed to determine the extent of the necrosis to declare itself.  Once this has occurred the unhealthy tissues is removed. This should reveal healthy tissue beneath.  The resultant wound is dressed and allowed to heal over time.  

Dr. ES

This will likely heal on its own without surgical intervention and with wound care. However, if the scar is excessively wide it may benefit from scar revision.

 Unfortunately this complication is a risk of tummy tuck surgery, especially in patients with a history of smoking. Your plastic surgeon will advise you on the best wound care, which typically involves a morning and night routine. It is important to achieve healthy tissue edges on all sides before any shrinkage in the dimensions will be apparent. This may involve debridements (removing any unhealthy tissue). Once the entire wound is free of necrotic or unhealthy tissue, then over time you will see shrinkage and healing of the area. Be patient! If a widened or depressed scar results, it can easily be revised later once the tissue is soft and supple to restore a good result. Sometimes the body heals so well, that over time scar revision isn't even necessary. 

necrosis usually occurs in the midline and can lead to separation of the wound. you  have the typical findings of black, hard, dry shoe-leather skin.  my concern is the drainage and greenish color. it is time to debride (remove dead skin) and wash out.  even colonization (not quire infection but bacteria present) can extend the zone of necrosis and lead to more tissue loss. intervention generally speeds recovery and allows the loss of tissue to be minimized. see you doctor. good luck 

This looks like a small area of skin necrosis which can happen because of numerous reasons.  It will probably heal on its own and may need a scar revision down the road.