Damaged trees seal themselves. It is not recommended to paint the wound. To help the tree repair damage and prevent infestations, you will need a saw and insecticide. The time required varies based on the severity of the damage.
Cut off damaged wood
Check the tree for any damaged wood that did not fall off. Carefully trim the loose wood, being careful not to cut into healthy wood. Dispose of the wood to prevent transferring disease to the healthy bark.
Water thoroughly to help the tree recuperate. The tree will form a callus around the wound, separating it from the rest of the tree. Water will continue to flow from the roots to the leaves in the surrounding areas. Deep and regular watering will speed the sealing process.
Apply an insecticide if pests threaten
Check the tree for pests common to the species. Apply an appropriate insecticide to prevent the pests from damaging the trunk any further. Wounded tissue is particularly vulnerable to pests and diseases, and should be treated aggressively.
Avoid treating with paint, emulsions, or wound dressings
Paint, emulsions and wound dressings can trap moisture against the tree, causing decay. Allow the tree to seal without application of these items.