The younger brother of Sri Lankan Test fast bowler Vishwa Fernando, Nuwanidu made his way through the national youth setup as a solid, right-handed top-order batter and useful off-break bowler. He attended St. Sebastian's College, Moratuwa, where consistent scoring in school cricket led to his selection for Sri Lanka's Under-19 team. He emerged as Sri Lanka's leading run-scorer in the 2018 ACC Under-19 Asia Cup, compiling 195 runs across five matches.

His domestic career began in December 2016 when he made his First-Class debut for Panadura Sports Club in the Premier League Tournament. Over subsequent seasons, he shifted to the Sinhalese Sports Club (SSC) and established himself across all three formats in Sri Lankan domestic cricket.

In May 2022, while representing the Sri Lanka Cricket Development XI on a tour of England, he made headlines by smashing an unbeaten 126 off 67 balls against Gloucestershire. Heavy run-scoring in domestic First-Class and List A tournaments for SSC and various regional sides earned him a reputation as one of the most technical young top-order prospects in Sri Lanka.

Fernando made his ODI debut for Sri Lanka on January 12, 2023, against India at Eden Gardens, Kolkata. He made an immediate mark by scoring a composed maiden half-century (50 off 63 balls) on debut. Later that year, he made his T20I debut against Afghanistan during the Asian Games in Hangzhou, China, in October 2023. Across 2024 and 2025, he remained on the fringes of the national white-ball squad, featuring in select ODI and T20I assignments, including Sri Lanka's bilateral series against New Zealand and Zimbabwe.

In the Lanka Premier League (LPL), Fernando has represented several franchises over consecutive seasons. He was drafted by the Jaffna Stallions for the inaugural LPL edition in 2020 before moving to Colombo Stars in 2021. He spent subsequent seasons with Galle Gladiators and Dambulla Aura, where he delivered notable performances, including a career-high LPL score of 63 not out in 2022. In the 2026 Lanka Premier League season, he featured in the top-order lineup for Jaffna Kings.