The Nikkei stock index plunged over 2 percent early Friday, tracking an overnight decline on Wall Street after Nvidia and other tech stocks fell despite the chipmaker's strong earnings report. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 1,233.67 points, or 2.48 percent, from Thursday to 48,590.27. The broader Topix index was down 22.59 points, or 0.68 percent, at 3,276.98.