The National Stock Exchange's index Nifty today regained the psychological 5,500 points level after a gap of 30 months, while the BSE Sensex shot up by over 88 points in opening trade on continued buying by funds.The 50-share NSE barometer Nifty gained 26.70 points to trade at nearly 30-month high of 5,505.85 points in the first five minutes of trade. Earlier, the index had crossed the level on 5th February, 2008.