Tyga is rolling around town with some sick jewelry — a diamond watch and chain worth more than $91,000 — but problem is the bling ain’t his … at least according to a lawsuit filed by a famous Beverly Hills jeweler.

In the suit, Jason of Beverly Hills claims the rapper agreed to drop $28,275 for the jeweler’s diamond pantheon watch back in August, 2012.

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JBH also claims Tyga — real name Michael Stevenson — borrowed a $63,000 diamond Cuban link chain in December, 2012 — but never returned the piece.

Now JBH is suing for the cost of both pieces, plus late fees … which just about doubles Tyga’s tab to a whopping $185,306.50.

We called Tyga’s peeps for comment … but haven’t heard back.

RICH FUN FACTS: Jason of Bev Hills has also iced up Justin Bieber, Mariah Carey, Diddy, Beyonce, and LeBron James. If nothing else, Tyga has good taste.

Source: tmz.com