Blac Chyna -- See, Tyga Ain't Doin' Nothin' with Kylie

Tyga is NOT hooked on Kylie Jenner ... at least if you believe what his baby mama just telegraphed.

Blac Chyna just posted a pic of her and Tyga all cuddly ... then almost instantly deleted it from her Instagram. The caption read, "by the way he said I'm not missin no meals" -- a reference to fine asses from "Anaconda."

The message ... he likes Chyna's ass ... NOT anyone else's.

Here's the rub. Tyga's been seen all over town with 17-year-old Kylie ... most recently on Tuesday, and it sure looked like a date.