小狗在玩耍时磕到了门槛。

Xiǎo gǒu zài wánshuǎ shí kē dàole ménkǎn.

The puppy bumped into the doorstep while playing.

走路要小心，不要磕着石头。

Zǒulù yào xiǎoxīn, bùyào kēzhe shítou.

Be careful when walking and don't bump into stones.

他走得太急，不小心把头磕在门上了。

Tā zǒu de tài jí, bù xiǎoxīn bǎ tóu kē zài mén shàng le.

He walked too fast and accidentally bumped his head on the door.