The Chelsea forward has been in fine scoring form on a club level over the last couple of seasons, but failed to find the back of the net in his first six appearances for La Roja.
That run came to an end during last night's Euro 2016 qualifier, however, when the 26-year-old registered his team's third of the match.
"We all wanted [Costa to score]. We've always been happy with his movement and he has worked well. He'll be very important in the future," Del Bosque told AS.
"Everyone wants to score goals and he linked up very well with Paco Alcacer. At half-time I told Diego that he needed to keep calm. He was a little nervous, not happy and not able to find a solution. When a player is so eager it's always ok."
Costa has scored nine times for Chelsea in the Premier League this season.