Rifnas capitalised on a defensive lapse in the final minute (90+4) of the added time to seal the win for Sri Lanka in the inaugural match of the championships.
The last man in the Nepal defence could not hold the ball and Rifnas emerged from behind to calmly shoot it straight into the net to give Sri Lanka a hard fought win in the Group A match at the Greenfield Stadium at Kariavattom here.
Sri Lanka take on hosts India on December 15 in their last group match.
The match was dominated by Nepal with chances coming their way but they failed to capitalise on them. Instead, they lost the match due to a defensive lapse in the end.