As of March 2021, she was ranked among top 60 athletes in the world according to World Athletics in the Road to Olympics rankings. She received the Universality Place from the World Athletics to compete at the 2020 Summer Olympics. She would represent Sri Lanka at the 2020 Summer Olympics in the women's 800m event and it marked her debut appearance at the Olympics. It was revealed that Nimali qualified to Tokyo Olympics only after Nilani Ratnayake had failed to qualify for the 2020 Olympics in the women's 3000m steeplechase. She was also the only Sri Lankan female track and field athlete to compete at the Tokyo Olympics. Nimali was also the first Sri Lankan track and field athlete to compete in women's 800m event at the Olympics after 29 years as Sriyani Dhammika Menike was the last to have competed in the relevant discipline. She could not proceed to the next round in the women's 800m after securing a 8th place finish in the heat event.