Killer Mike‘s officially putting his arrest at the Grammys on the back burner, because after a long wait, his oldest son is finally getting a kidney transplant … 360aprokoHip Hop has learned.

Sources connected to the Grammy-winning rapper tell us Mike is with his son Mikael “Pony Boy” Render Monday as he undergoes the transplant surgery. The 21-year-old has been waiting for a kidney match for 3 years.

Back in November, Mikael got bumped up on the transplant waitlist, and his proud dad talked about it during an interview with Graham Bensinger.

Mike has said Mikael — who’s a musician and rapper, just like Dad — never had a chance to fully experience his teenage years, because of his battle with kidney disease.

The fact Pony Boy’s number got called for the transplant today, of all days, seems like a strange twist of fate … considering his dad’s weekend of some major ups and downs.

360aproko broke the story … Killer Mike was awarded 3 Grammys Sunday at L.A.’s Crytpo.com Arena — but he also got arrested.

He was booked for misdemeanor battery after allegedly knocking over a security guard at the venue, but was quickly released on his own recognizance. After getting released … Mike was in relatively good spirits, even though he’d gone through a fairly dramatic situation.

Paps tried talking to him about it in the aftermath — but he wasn’t really trying to talk much about it … keeping his attention on the music. In light of this news about his son … his mind was clearly elsewhere, as he had more important matters to attend to.

Mike won Grammys for Best Rap Album, Best Rap Song and Best Rap Performance — but today his focus is purely on Mikael’s surgery.

Here’s hoping all goes well on that front.