According to the idiom, what do you bite when doing something unpleasant?

"Bite the bullet" is an informal phrase that means "to do something unpleasant or painful because it is necessary even though you would like to avoid it." For example, you may not want to spend a lot of money on a new car, but if you know yours is beginning to break down a lot, you might have to bite the bullet and buy a new one. For example: "Their manager had been putting off the budget meeting but decided to bite the bullet and have the meeting this week."

Source: Britannica