Grosjean appeared to move across on Hamilton on the run towards La Source, putting the McLaren on the grass.
Hamilton said he just wanted to move on and celebrate team-mate Jenson Button's victory.
"I don't want to talk about the start crash," he said.
"Just congratulations to Jenson, he did a fantastic race. It looked like a walk in the park for him."
While Button took a commanding pole position and race win, Hamilton only qualified eighth following a controversial decision to stick with an older-specification rear wing.
"It's great to see that the team had the pace and I've got to try to pull that out of my car in the next race," said Hamilton.
The start incident saw Hamilton, Alonso and Grosjean's cars all slightly airborne at times, but the Briton played down the severity of the crash.
"I've had a lot worse than that," he said.