"It's obviously very frustrating that I can't play.
"Early on I had a lot of headaches and it was hard to concentrate.
"But I'm a lot better now and probably a couple of weeks away [from playing].
"It is just taking its time but I have to make sure I look after my head because I only get one."
Asked by a pupil if he would be playing in the Lions tour, Coles said, "Yep that's the plan.
"Hopefully I'll be back so I can get the chance to play against the Lions."
Coles, 30, spoke about growing up in Kapiti and attending Paraparaumu Beach School and then Paraparaumu College.
He started playing rugby at about the age of 5 for a team called the Beach Veges.
"We were sponsored by a vege shop in Pram Beach and used to get free oranges at halftime and stuff like that."
Coles, who loved watching All Blacks games on television with his father, made Paraparaumu College's 1st XV in his fourth-form year.
"I guess I was one of the biggest guys going around and they needed a front rower."
Soon he was in the Horowhenua under-16 team and then, after impressing at a regional tournament in Taranaki, made the New Zealand U17 side.
He left Paraparaumu College in his final year, because of a strong desire to play division one rugby, and went to Wellington College.
"I had no friends for about the first two months and would eat lunch by myself."
After leaving school he made the Wellington Rugby Academy team and played for Poneke.
"I also worked for four years and was pretty much a labourer."
He made the Wellington Lions team in 2007 and then the Hurricanes in 2009 where he was Andrew Hore's understudy for three years.
"After he [Hore] left I had the opportunity to start [for the Hurricanes] and kind of never looked back."
Becoming an All Black was a special moment.
"I was playing for the Wellington Lions and we had just been knocked out in a semifinal and they weren't naming the All Blacks for about a week or two.
"There had been a bit of talk [about his possible selection] and I was just sitting at home, trying to keep busy and not think about it.
"The team was going to be named on television so I was watching it but it wasn't on and then someone texted me congratulations so I went online and found out.
"It was a surreal moment.
"Ever since I was probably one of you fellas sitting here I had wanted to be an All Black."
Now a key member of the Hurricanes as well as the All Blacks, Coles said he was "living the dream" of being a professional rugby player.
"It's something I've always wanted to do."