Courtney Stodden went under the knife for her second nose job ... and she tells TMZ this time it was more than a cosmetic procedure.

Here's the deal ... Courtney posted a red-hot bikini thirst trap on Wednesday to highlight her surgery and ongoing recovery.

Courtney tells us ... she was not happy with her first nose job -- and she could not breathe as well as she expected afterward ... but that all changed after this operation.

Shouting out her surgeon -- Dr. Gary Motykie -- CS says she can breathe easier thanks to the breathing correction that accompanied the rhinoplasty and some facial fat grafting. Gallery Launch Gallery Twitter/Instagram

All in, she dropped about $20K on the new sniffer ... which she says is quite reasonable given Hollywood prices.

Courtney also not

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