Major bummer! There is not one thing you can do. No painting or sealing. All you can do now is wait to see if what got left for the vascular system will be able to deliver enough water and chemicals to support the canopy above that damage.
Where is it that you live? Have you ever used the Cooperative Extension Service of your nearest University? One thing you could actually do is to call them to get an arborist out to check this tree. Very inexpensive.
I'd also call your Homeowner Association. This looks as if it is in your front lawn which is also under the auspices of your HOA. If this is one of the 'street or frontage' trees they are kind of in charge. Appearance is everything to the HOA. They dictate what kind of trees are in the front yards, the colors of the homes...I am guessing a Linden tree?
If the canopy above that damage is fairly large...looks like it might be...this tree could also be deemed dangerous. Check these two organizations out and let us know what they say. Another picture of the entire tree would be very helpful, as well as a closeup of those leaves!