2 sentences

1. 这支钢笔的笔尖戳坏了。

   zhè zhī gāng​bǐ de bǐ​jiān chuō huài le.

   The tip of this pen is broken.

   Source: Dong Chinese Dictionary

2. 你在给这个图案填色的时候，笔尖注意不要出线。

   nǐ zài gěi zhè​ge tú'àn tián​sè de shí​hou, bǐ​jiān zhù​yì bù yào chū​xiàn.

   When coloring this pattern, be careful not to let the tip of your pen go outside the lines.

   Source: Dong Chinese Dictionary