If there is some defect in the nose and the purpose of the cosmetic surgery is to remove that defect, then there is nothing wrong with nose jobs (rhinoplasty). But if the purpose is simply to make it more beautiful, then it is not permissible to do this cosmetic nose surgery.

In Islam, hair transplants for baldness are permissible as they fall under restoring what was naturally lost, not altering Allah's creation.

It is not permissible for men to have gold teeth fitted unless that is essential because it is haram for a man to wear gold or adorn himself with it.

You can pray with nail polish unless the nail polish contains a substance that prevents water from reaching what is beneath it.