A fine amateur boxer, he logged 50 wins in 52 contests before joining the paid ranks in 1979. In only his 14th pro bout, he was matched as a late substitute with Hall of Famer Salvador Sanchez for the WBC featherweight belt in Madison Square Garden. Nelson battled the Mexican legend valiantly before succumbing in the 15th round of their July 1982 contest.
The previously unknown Ghanaian was now a recognized force in the 126lb division and on December 8, 1984 he captured the WBC championship with a 11th round TKO over Hall of Famer Wilfredo Gomez. He successfully defended the belt six times before winning the WBC super featherweight title from Mario Martinez in 1988. After four title defenses, he unsuccessfully challenged Pernell Whitaker for the WBC/IBF lightweight titles. Upon returning to the 130-pound class he defended his championship six more times, including a controversial draw with Australian Hall of Famer Jeff Fenech on June 28, 1991.
In the rematch eight months later, Nelson ventured to Australia and stopped Fenech via 8th round kayo. Wins over Calvin Grove and Gabe Ruelas led to the first of four encounters with "Jesse" James Leija. Nelson drew with Leija in their first bout on September 10, 1993 before losing the WBC title to the tough Texan in the rematch eight months later. After regaining the belt from Leija's successor Gabriel Ruelas in December 1995, Nelson got revenge with a TKO win over Leija in the 6th round of their rubber match. In his next outing he lost the championship to Genaro Hernandez (L12) and then dropped a 12-round decision to Leija in what would be Nelson's last bout.
A true world champion, he fought all over the globe, including England, Australia, Spain and Mexico and throughout the United States. A combination of technical boxing skills, power in both hands and a reliable chin enabled Nelson to compile a 39-5-2 (28KOs) record. A national hero in his homeland, Nelson still resides in Accra.