Codlin moth. Very hard to deal with. Just picked 40 kilos of apples and threw away nearly all of them because of the moth larva in them.
Various things to try. Grease bands on the trunk and branches in June/July. This is to catch the grubs as they leave the fruit to pupate. Bit late as they will already have damaged the fruit.
Pheramone traps to catch them. Only reduces the population and is mainly used as an indication of when to spray against them.
Spray the tree with Winter Wash in February to kill off the pupating larva. Again, this only reduces the numbers.

I had this problem last year and most of my (over 100) apples were thrown away. And while I carried out the advice I had last year - including inspecting the tree several times a day during the appropriate months - some have been ruined again this year.
Take great care next year as directed in the reply above.

You can actually use the apples. We often slice them up and only use the non infected parts for purée etc.

Thanks OB, I realised that this year, and rescued up to 3/4 of my infected apples.