Have you ever read about what it's like to get an IUD inserted? I would recommend checking that out and then asking whether a small injection to the genitals is really the worst possibility.
I'm sure nothing could be worse. You're welcome to volunteer to get either procedure, both, or neither. I would recommend elective medical procedures stay optional.
An ex-gf of mine gently flicked my gonads once without warning, that was no picnic either. Luckily, just like an IUD, it isn't mandatory. Horses for courses.