He has served in several senior positions in the Foreign Ministry of post-Apartheid South Africa. Since February 2012 he has been South African Ambassador to the Kingdom of Belgium, the Grand Duchy of Luxembourg and the Head of Mission to the European Union. An expert in the field of international relations and diplomacy, Nkosi previously headed Africa Branch in the Foreign Ministry.
He has travelled extensively in Africa, and accompanied high-level delegations of former President Thabo Mbeki, President Jacob Zuma, former Foreign Minister Nkosazana Dlamini-Zuma and Minister Maite Nkoana-Mashabane.
Before joining the government, Nkosi was a trade union leader, where he served as the Deputy General Secretary of the South African Democratic Teachers Union (SADTU), an affiliate of the Congress of South African Trade Unions (COSATU). Nkosi was a student and youth activist in Soweto, occupying several leadership positions in the Azanian Students" Congress (AZASO) and in the South African Students" Congress (SANSCO).
Trained as a teacher, Nkosi holds a Master"s degree in International Relations and Diplomacy.