Sema was born in P. Vihoto in the Niuland district, Nagaland. He joined as a havildar in the Indian Army and was promoted as Naib Subedar with 9 Assam Regiment.[7] He lost his leg in 2002 during an operation at the Line of Control due to a landmine blast. At 32, he started shotput and trained under coach Rakesh Rawat.[1] He is currently supported by Olympic Gold Quest, a sports NGO.