I just made ice cream. Unfortunately, it became gritty in the end result. What is a way to make use out of it?

Given all of the advice so far, and as you said that you started with a rather large batch, I might try a few things. I would recommend trying a small-ish portion at a time, so you don't ruin the whole batch:

1. Soften the ice cream slightly, then put it through a food processor to see if you can make it less gritty, then re-freeze. (or possibly don't re-freeze, if it has a soft-serve like consistency)

2. Soften the ice cream slightly, then mix in other ingredients to add texture to the ice cream to try to hide the grittiness. Nuts, cookie or pretzel bits, or anything else that's crunchy. You could also make an 'ice cream pie', but you'd want a rather thin layer of ice cream so it's not so obvious that it's not cream. (maybe something like this

3. Scrape it with a fork, and tell people it's a granita. (or, actually make a fruit granita, and then serve it layered with granita / scraped ice cream / etc.)

4. Melt it down, add starch and cook into a pudding, then re-freeze. (frozen pudding also has a strange texture that isn't quite ice-cream like).

5. Melt it, add some more eggs, then use it as the custard for french toast or bread pudding.

The texture will be as a result of ice-crystal formation.

During ice cream manufacture you are basically cooling a mix of cream and sugar and aiming to make an emulsion that reduces the ice-crystals into small enough bits that they feel smooth. Churning and cooling are the two things that allow this to happen. Churning mixes air and water into the cream (fat) creating tiny bubbles known as lipospheres that freeze solid without creating much in the way of ice.

Your grittiness is likely to be a direct consequence of making a large batch and the machine not being able to churn it properly for long enough or churning it incompletely, or perhaps as a result of it being difficult to chill to the right temperature quickly enough. Ice crystals will grow under any of these conditions.

You may be able to re-process it, basically soften (maybe melt) and split into smaller batches, then re-churn. as @Rumtscho has pointed out in his answer and comment you can't actually do this.

You are not going to make it creamy. Re-freezing will give you up worse crystals, even if you try to change something about your process.

If you don't want to eat it frozen, you have to thaw it and drink it as a milkshake, or use it as a sweet custard sauce.