I believe the damage on your apple is from an apple curculio. You would not see insects now because they would have been present when the apple first started forming. Picking up and destroying apples that have fallen will reduce numbers next year. There is also a spray regimen following bloom time in the spring that can be used. Below is an portion from a UMN publication that gives information regarding apple curculio.                           


Apple curculio

• Occasional cause of “wormy” and dropped fruit.
• It is a species of weevil; adults have a distinctive snout and are red to brown in color.
• Adults lay eggs inside developing apples shortly after petals fall, which causes scarring on the apple’s skin. If you are treating trees for plum curculio, apple curculio may also be controlled.
• Larvae burrow into the fruit to feed on the developing seeds, causing apples to rot and drop off of the tree.
• Adults wait out the winter in sheltered areas.
• Removing dropped fruit helps reduce next year’s population.
• Spraying for plum curculio shortly after petal fall also manages apple curculio.