NFL Star Donte Whitner -- Gotta Pay NIKE Before He Can Change Jersey to 'Hitner'

Before 49ers safety Donte Whitner can officially sport a "Hitner" jersey on the field, he's REQUIRED to get Nike's blessing ... and it could cost the player a ton of money.

By now you know, Whitner's vowed to legally change his name to Hitner after the NFL fined him $21k for an illegal hit on a St. Louis Rams player earlier this season.

But it's not gonna happen for AT LEAST another month, because the NFL requires players to legally change their name before they can change their jersey. And in Donte's home state of Ohio ... an applicant has to publish a notice of the name change in a widely circulated publication at least 30 days before a judge will even consider signing off on the move.

Court officials in Ohio tell us the process usually takes AT LEAST six weeks from start to finish.

Then, there's the Nike factor -- an NFL rep tells TMZ before the league will allow a player to change the name on his jersey, he has to purchase any remaining Nike inventory featuring his old name.

But whatever the cost, Donte can probably afford it -- he's reportedly raking in $3.8 million this season.

So, if all goes according to plan, you could see a Hitner jersey on Nov. 17 ... when the 49ers play the Saints.