Nieto, who was waived by Pittsburgh on Feb. 26 and cleared, has played eight games in the AHL with one goal and two assists.
The 32-year-old winger played 31 NHL games for the Penguins this season, averaging 12:14 of ice time and recording one goal and two assists.
He's in the last year of a two-year deal that's paying him $900,000 per season but has missed considerable time recovering from several knee surgeries.
Aho, on the other hand, is dressing for the NHL club for the first time this season. The defenseman, who has played 190 games for the New York Islanders in the NHL, inked a two-year deal with the Penguins during the offseason that pays him $775,000 annually.
Though he came into camp hoping to win a spot on the roster, he was assigned to the AHL and has been there for the duration of the season.
Injuries have affected Aho's status with Wilkes-Barre/Scranton, yet the 5-foot-11 left-shooting blueliner has appeared in 17 games with seven assists.