Born in Treviglio, Lombardy, Nossa started his career with Internazionale, one of the biggest team in Lombardy. In 2002, he was promoted from Allievi Nazionali to senior youth team – Primavera. He finished as 2 consecutive Primavera League runner-up in 2003 and 2004 as vice-captain. Started to play as a central defender, he also played as a right winger and right back for the "Primavera" team. He also call-up three times for the first team in competitive matches, wore no.34 as unused bench against Juventus in 2003–04 Coppa Italia, against Sochaux as unused bench in 2003–04 UEFA Cup. and against Brescia in 2003–04 Serie A. Nossa made his debut and only appearance for the first team on 31 May 2003, substituted Marco Materazzi in the second half. The friendly match ended in 1–0 win against Fiorentina