Eating an unripe Avocado won't harm your health or make you very sick.
But if you do eat an Unripe Avocado it might lead to stomach aches or diarrhea but most times you won't even experience any problems when eating the unripe Avocado.
Although unripe Avocados do not taste as good as fully ripe Avocados do but it's certainly safe to eat unripe Avocados but some peoples stomachs may be more sensitive and may experience the stomach pain or diarrhea.
But there's nothing to worry about when eating an unripe Avocado and you're not gonna be harmed.