This is a big open space, and it will take time for the callus tissues to form. Do not put black paint, etc. on this wound. Let it heal naturally. I've got six tomatoes in my back yard and some type of bug is helping itself to its own gourmet salad. Make water available near the garden.
Squirrels eat the tomatoes to get water.
Opossums also will eat tomatoes. Another possibility is black birds or crows. Usually, they punch holes in the fruit but don't often take the entire tomato. These white spots are a powdery mildew fungus that likes to invade the leaves of many plants, including crape myrtle, roses, zinnia, bee balm and lilacs. The fungus thrives on cool nights and warm days.