A Hunter Valley woman remains in pain and awaiting skin grafts after she suffered severe burns when sinking into hot ash in freshly burnt bushland.

Key points: Rachael Peters fell into knee-deep ash when attempting to put out a burning stump at a Hunter Valley bushfire site and struggled to escape

Rachael Peters fell into knee-deep ash when attempting to put out a burning stump at a Hunter Valley bushfire site and struggled to escape Her 10-year-old son, who has autism, was left distressed after witnessing the incident

Her 10-year-old son, who has autism, was left distressed after witnessing the incident Mrs Peters is on strong medication for the pain and due to have skin grafts on her legs and hands tomorrow

Rachael Peters was trailbike riding at Stanford Merthyr, near Kurri Kurri west of Newcastle, on Sunday when she went to put out a burning tree stump in the remnants of the Pelaw Main fire, which started after a fatal car crash back in early December.

But she is now awaiting skin grafts for her legs in Sydney's Royal North Shore Hospital after she fell into knee-deep ash.

Mrs Peters' mother Patricia Kew said her daughter was riding with her husband and their ten-year-old son when the accident happened.

"She saw a few little flames in this tree stump … the [Pelaw Main] fire had been burning for three weeks," Ms Kew said.

"She thought she would do the right thing and go down and smother it so it didn't spread.

"So she jumped down the embankment, which looked like hard ground, but it was all ashes.

"When she tried to get out she couldn't, she just kept sinking."

Father and son watched on helplessly as she fought her way out, slipping and burning her hands in the process.

"They couldn't get to her," Ms Kew said.

"I asked her how the hell she did manage to get out, and she said she just gave it her all and reached the top of the hill."

A single vehicle car crash sparked the fire near Cessnock. ( ABC Newcastle: Ben Millington )

Family reliving the nightmare

The family rushed to Kurri Kurri Hospital and Mrs Peters was later taken by ambulance to Sydney's Royal North Shore.

"You could tell the shock started to set in [at Kurri Kurri Hospital] when she started crying," Ms Kew said.

"I kept hosing her down in the shower but the water wasn't cold enough, so once we got her onto the bed her hands were in such pain, we kept getting all the cold water out of the drinking machine and pouring it over her.

"We had to cut all her wedding rings off because it started swelling.

"It was terrible to see your daughter in that much pain. They could hear her out in the waiting room."

Patricia Kew said the ordeal was "very distressing" for all of them.

Rachael Peters and her 10-year-old son. ( Supplied )

"Her little boy, he's got really bad autism, and he stood at the top of the hill and has seen everything," Ms Kew said.

"He was pretty traumatised last night.

"He got up this morning and was still talking about it."

Rachael Peters burnt her hands as she slipped and struggled to escape knee-deep ash at the site of the Pelaw Main bushfire. ( Supplied )

Mum warns of ash danger

Ms Kew said Mrs Peters was "still in a lot of pain" and on strong medication and due to have skin grafts on her legs and hands tomorrow.

The family is urgently warning others to avoid the same ordeal.

"She thought it was a hard surface she was jumping down onto and it wasn't," Patricia Kew said.

"I know a lot of people go out there motorbike riding with young kids. People take their animals for a walk out there.

"It should be sectioned off or there should be a sign or something … it would be so easy for a child to walk down on there.

"I went to bed last night just having a vision of her trying to climb out of this hot ash, and thinking to myself, 'What if my grandson had jumped down there as well?'"