sasu
1.

To forcefully insert a sharp, pointed object into another object, causing it to penetrate its surface.

2.

To inflict harm by piercing someone's body with a long, sharp object, often with malicious intent.

3.

To kill or attack by thrusting a weapon into the body of another.

4.

To use a needle to sew by pushing it through fabric or material.

5.

To apply a sharp or intense stimulus to the senses, such as sight, smell, or touch, often causing discomfort.

Example:

蚊にたくさん刺されました。

tsukisasu
1.

To forcefully penetrate a surface with a pointed object, often resulting in a piercing or impaling action.

2.

To sharply provoke or evoke a strong emotional or physical reaction, akin to the sensation of pain caused by a piercing object.

3.

To sharply insert or insert forcefully into something, typically with the intention of causing an effect that goes beyond mere contact.

Example:

彼はミートボールにフォークを突き刺した。