Nadal, the world number one, struggled with the problem during his Australian Open final defeat to Stanislas Wawrinka but seemed fully fit as he ousted his fellow Spaniard in straight sets.
"Daniel is a specialist on clay, so for me it was a great match after so much time off after the final in Australia because of the back problems," Nadal said.
"I practiced very little. So I was happy to get back, and get back with a victory."
The event in Brazil boasts many of the world’s best clay-court players, with second seed David Ferrer also progressing with a 6-2 6-3 win over Frenchman Jeremy Chardy.
"For Rio, for the Brazilian people, for everybody it's nice because he's No. 1 in the world," the Italian said. "For the tournament, especially because it's the first year, I think it will help."
1-Rafa Nadal (Spain) beat Daniel Gimeno-Traver (Spain) 6-3 7-5
2-David Ferrer (Spain) beat Jeremy Chardy (France) 6-2 6-3
Pablo Cuevas (Uruguay) beat Alejandro Gonzalez (Colombia) 6-7(0) 6-1 6-3
7-Juan Monaco (Argentina) beat Horacio Zeballos (Argentina) 6-3 6-1
4-Tommy Robredo (Spain) beat Pablo Carreno (Spain) 7-6(5) 6-3
Joao Sousa (Portugal) beat 6-Marcel Granollers (Spain) 2-6 6-3 7-5
Alexandr Dolgopolov (Ukraine) beat 5-Nicolas Almagro (Spain) 2-6 6-3 6-0
Albert Ramos (Spain) beat Leonardo Mayer (Argentina) 6-2 6-0
8-Pablo Andujar (Spain) beat Julian Reister (Germany) 6-4 6-3