The 30-year-old fashion designer, who got engaged to her long-term boyfriend James Rothschild earlier this month, was spotted flashing the diamond sparkler while strolling the East Village neighbourhood of New York City.
Dressed in a black-and-white patterned dress, Nicky showed off her long legs in a thigh-skimming frock. She completed her monochromatic look with black lace-up boots and shades, and accessorised with a leather satchel.
It was hard to miss Nicky’s Asscher-cut diamond ring, which appears to be set in a platinum band and fits perfectly around her ring finger.
“Nicky’s ring looks to be a five-carat Asscher cut diamond in the centre with two trapezoid diamonds on either side,” said expert David Allen at 77 Diamonds in London.
“The nature of an Asscher cut means you really need to get the highest quality in order to feel the true beauty of the stone so a ring of this calibre and size would be worth around $450,000.”
Read more: The best celebrity engagement rings
Nicky’s banker fiancé James popped the question when the lovebirds were on holiday, celebrating their anniversary with a road trip around Italy.
“They are both really excited and incredibly happy,” a source told US Weekly. “He took her out on a boat into the middle of Lake Como and he proposed, got down on one knee and everything. It was incredibly romantic and beautiful.”