I have a young apple tree and it has fruit for the first time, but most of the apples have this in them. Any advice would be welcomed.
This looks like apple maggot to me. A very very normal and regular pest. The adult lays the eggs in the epidermis of the fruit bud or the new apples. they hatch and eat their way out of the apple. Cleaning up the apples on the ground, leaf debris would be the best management. There will always be a few apples that have Apple Maggot no matter what you do but leaving apples lying on the ground could easily cause all of your apples to have this.
Just have to eat around the maggots? Grins!!