@AKEmon869 suffering can be infinite because beyond the physical pain itself, it's a thought that can be recursive and reinforcing.
For example, you can go broke (pain) and then either work your ass off to pull yourself out of poverty or embrace minimalism and be happy with less.
Or you could imagine a scenario where you're a victim and it's everyone else's fault but yours, and do nothing but bitch about how much you hate those responsible.
The latter scenario involves infinite suffering.