Nicol contributed significantly to diabetes research from his discoveries in his analysis of the breakdown of insulin in the human body.

He taught at the Prince of Wales School in Freetown, the capital city of Sierra Leone, and studied on a scholarship at Christ's College, Cambridge University in the United Kingdom, graduating with a BA degree in natural science in 1947.

[2][3] In the early 1950s, he taught at the Ibadan University medical school, researching topical malnutrition, before returning to Cambridge in 1954.

Nicol left academia in 1968 to become the permanent representative of Sierra Leone to the United Nations (UN), in which role he served until 1971.

While holding this post, Nicol additionally served as head of the United Nations Institute for Training and Research (UNITAR).

[6] He maintained a home for many years in Thornton Road, Cambridge, England, frequently visiting Christ's College, of which he had been made a distinguished Honorary Fellow, meanwhile serving from 1987 until retiring in 1991 as a visiting professor of international studies at the University of California (1987–88) and University of South Carolina (1990–91).