All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If by enhancement operation you mean returning your nose to its natural state as it was before it was brocken, then it is permissible to undergo this enhancement as this falls under seeking treatment. Indeed the Prophet said: "Seek treatment, indeed Allaah has not sent down any illness without sending a cure for it." [Ahmad, Abu Daawood and At-Tirmithi]
However, if by undergoing this operation you only want to beautify your nose without any change or deformation in it from the state it was before breaking, then this falls under changing Allaah's creation and this is not permissible.
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Allaah Knows best.