Tyga had better ante up A LOT of money he owes to his old biz partner, 'cause if he doesn't ... Sheriff John Brown could come knockin' for the dough ... now more than $2 mil.

Tyga's former business associate, Chuon Guen Lee, just filed docs with L.A. County Superior Court asking a judge for an assist in collecting a $1.9 million judgment she won against him last year ... which has now ballooned to $2,148,411.

You'll recall ... Tyga was sued by Lee in 2015 for allegedly stealing their t-shirt idea for a company they were starting at the time called Last Kings. Welp, he lost that lawsuit ... and was ordered to pay up.

Lee's saying she hasn't been able to track down Tyga.. If the court signs off on her request ... Tyga might get a visit from a sheriff's deputy.

We've reached out to Tyga for comment ... so far, no word back.