He said his father had lost a lot of skin on his calf muscle.
"It's about how it heals and how the skin grows. An 85-year-old has pretty soft skin. But he's faring pretty well."
Phil Lester, his other son, was travelling from overseas to be with his father.
New Plymouth Department of Conservation partnership manager Darryn Ratana said the seal was still on an isolated beach this morning.
"We have a cordon around him and we are still monitoring him. He may well stick around while the sun is still shining. He seems pretty calm and as long as people stay away from him, he's not a danger to the public."
He hoped the seal would swim out to sea when the high tide came in.
Mr Ratana said DoC staff had visited the victim.
"He was stable and we hope he has a speedy recovery.'
He said the bite was "pretty nasty one. There was an awful lot of blood."
The seal was a young male between 100kg and 150kg, Mr Ratana said.
"They can be quite aggressive. He's alone. They're wild animals, so people should always be wary of them."
He said putting the seal down would only be a "last resort" and only if there was an imminent threat to public safety.
"They are protected species, and we would only look to destroy an animal in consultation with police, and only if there was an immediate public threat."
The walkway was very popular and there would have been tens of thousands of people there during the holiday weekend, he said.
"It was a very narrow part of the walkway, so we'll be in discussions with the New Plymouth District Council this coming week to see if more signage might be required, just warning people to stay clear of these animals."
