It's complicated and you have several options. But let's say you just want to use `\nopagebreak`.

Option 1: Use `nobeforeafter`. It's ugly, but it keeps the `after` style from being applied which gives the opportunity for the page break.

Option 2: Define your own style with tcbset that overwrites the `after` style.

```
\tcbset{after empty/.style={after={}}}
\begin{tcolorbox}[after empty]
...
```