Why did Chandler react so much at the end of Friends Season 3 episode 14? What do you mean?

Chandler's girlfriend, Singer, has a prosthetic leg. Chandler doesn't think it's a big deal to install a prosthetic leg, but Singer dumped Chandler after discovering that he had a third nipple. Finally, Chandler had an operation to remove the third nipple.

Then come back and tell my friends that I just had a minor operation. Two nipples. Don't wait.

Monica made a joke at this moment: Wow! Just like Rachel in high school, Rachel in high school is like this.

However, Chandler, who has always claimed to be the king of jokes, did not understand the joke. He suspected that the third nipple inspired his humor, and now his talent has been lost after the operation. He said: the source of all my strength. Oh, dear God, what have I done! The source of my talent. God, look what I've done. A little scared and regretful.