She bit down hard on the cold material but for nothing.

He bit down hard on the inside of his lower lip.

She bit down hard on the inside of her cheek.

He bit down hard on the inside of his cheek.

He bit down hard on his lower lip to make himself stop.

Looking away, Mary bit down hard on her lower lip.

To keep from screaming, she bit down hard on her lip.

She bit down hard on her lower lip to keep from screaming.

Bite hard on this, and make sure your tongue is out of the way.

He bit down hard on his lip and tried not to notice the smell.