The New Zealand captain was born in the devastated city, where 98 people are known to have died and more than 220 are still missing.
Nelsen, 33, sent BBC Sport a text saying: "Family and friends all ok."
He also confirmed his sister gave birth to a son after being "knocked over" by the quake and going into labour.
Nelsen and wife Monica learned about the earthquake while at home in Cheshire and the Blackburn club captain had to wait anxiously for news of his sister at Rovers' training ground on Wednesday.
It was an incredible feeling of helplessness. It was horrible. It's a weird feeling.
Ryan Nelsen
He told New Zealand newspaper
The Dominion Post:
"Monica checked the telephone for messages and said 'Oh, my God'. We turned on CNN and tried to make phone calls [to Christchurch] but we couldn't get through for ages.
With his sister, Stephanie Martin, 37 weeks pregnant, the tension was even greater.
"It was such a relief to get that text from mum to say everything was OK," explained Nelsen, who left New Zealand to play football in the United States in 1997.
"It was an incredible feeling of helplessness. It was horrible. It's a weird feeling.
"I said to my wife, 'I've been away from home for 14 or 15 years, and you get homesick, but I've never felt that I wanted to be back in Christchurch as much as I did [on Wednesday]'. I just wanted to be there for my family and friends."
Nelsen, who joined Rovers from US side DC United in 2005, will be available for selection for the Ewood Park oufit's Premier League game against Aston Villa at Villa Park on Saturday.
Source: BBC Sport
Source: BBC Sport