Those "sharp things" were nails which were still attached to a piece of wood from the burn-off.
"They were rusty and poking straight up," Macpherson said.
"It was right where we were walking and the dog had just been straight through there once. It was kind of like running through a minefield.
"I don't know how many pallets were burnt but there were easily hundreds of nails."
He and another beachgoer spent an hour uncovering and collecting the nails but Macpherson said there was no way of collecting them all by hand.
He posted about his discovery on local Facebook pages in an effort to advise people to take care in the area and to encourage those burning wood to check what might be left behind.
He has also contacted Tauranga City Council to see if it can organise for the nails to be cleared.
"It looked like it had been covered in sand after the fire," he said.
"So they did everything right, except they used wood with nails in it. It is worrying to think of dogs or kids running around on that beach with those there."