'I was down the paddock mate with my Akubra on, my flannos', just slamming away on a star picket with a huge sledgehammer and twang - away it went,' Grant told hosts Ed Kavalee and Ash London.
He later confirmed he was trying to hammer a post into the ground with a mallet when the injury happened.
‘I'm trying to grow some trees and these trees need to be held up by posts,’ Grant explained.
The star’s injury means he’s unable to host Dancing With the Stars on Monday and his wife Chezzi Denyer also spoke to the show to say the incident had caused her to suffer ‘flashbacks’ to a previous life-threatening injury he suffered during a car accident in 2008.
'In hospital... yeah there were a few flashbacks there! Especially after they gave him Morphine,' Chezzi told the show.
We wish Grant a speedy recovery.
LISTEN: Grant Denyer Reveals His Drug Hallucinations as He Admits His Wife Chezzi 'nearly Left Him'