Real moved within three points of La Liga leaders Barcelona and second-placed Atletico Madrid - who played out a goalless draw on Saturday - thanks to a 55th minute header from the Portugal defender.
And the 30-year-old hailed the importance of the victory as Real look to regain the title after finishing well behind Barca last season.
"I helped my team with the goal," he told Canal +. "But the most important thing is we fought a tough match against a fighting team.
"We knew it was important to win because (Atletico and Barca) tied yesterday and this win closes the gap."
Pepe's compatriot and team-mate Cristiano Ronaldo could be announced on Monday as the winner of the Ballon d'Or, a prize Pepe feels the former Manchester United man is worthy of.
"I would vote for Cristiano because what he did last year was very important," Pepe added. "He deserves it."
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