So you messed up. It happens. You brought home a green rock. Don’t panic. You can sometimes leave it on the counter for 1-2 days at room temperature. It won’t ripen like a banana, but it might soften a little.
Be warned: it will never become truly sweet if it was picked too early. But hey, you can cube it up, toss it with some lime juice and mint, and it’s a respectable salad base. Lime juice fixes everything, including bad fruit decisions.
Or, just blend it with some coconut water and call it a “smoothie.” The blender forgives all sins.