Nicki Minaj and Kenneth Petty's Wedding was No Frills, Big One to Follow

Nicki Minaj and Kenneth Petty only got hitched because the clock was ticking on their marriage license ... and they'll have a big bash with friends and family later.

Sources with direct knowledge tell TMZ ... Nicki and Petty got married Monday at a private space in L.A. We're told the only people who attended -- aside from the bride and groom -- was the minister.

As for why the rush ... their marriage license expires at the end of this month, so they had to pull the trigger or start all over again at square one. It's only good for 90 days.

Our sources say Nicki and Kenneth are going the route of Justin and Hailey ... a small, no-frills wedding followed by a church service and massive celebration. As for Nicki and Kenneth ... we're told they're in no rush, but they will plan a big event.

Nicki posted custom bride and groom hats and mugs Monday with the date engraved ... a glimpse into the day's festivities.

Our sources say Nicki and Kenneth were already living as hubby and wife ... even referring to themselves as married, so this isn't a real big change.