Posting on Instagram to thank all those who sent her well wishes after giving birth - including Beyonce, Kim Kardashian and Kanye West, and Winnie Harlow - she wrote: "Thank you to Queen B, Kim & Ye, Riccardo Tisci, Winnie, Karol & everyone who sent well wishes during this time. It meant the world to me.
"I am so grateful & in love with my son. Madly in love. My favorite liddo boy in the whole wide world. (sic)"
The 37-year-old rapper - who was reported to have welcomed her son on September 30 - has chosen so far to keep her son's name private.
Nicki revealed her pregnancy back in July with a series of Instagram posts showing off her baby bump, one of which was captioned "#preggers".
The "Chun Li" rapper first sparked speculation about her pregnancy in May after discussing her food cravings and feelings of "nausea".
Nicki listed the bizarre food combinations she had been cooking up, and said that whilst she had not been throwing up, she felt sick and had been going to the toilet more often than usual.
When one fan asked her if she had been cooking anything in recent weeks, she said: "Absolutely. Steak. Shrimp. Plus my famous cheeseburgers. So good. Been rlly having red meat cravings then salad cravings with extra jalapeños. Ordered Chkn nachos that didn't come w/jalapeños. Who does that? Wow. (sic)"
