The 26-year-old's season has been hampered by crashes and he claims that he is continuing to work on eradicating his mistakes with Lotus.
"It was a stupid mistake," Grosjean told the official Formula 1 website. "Mark came to see me after the race and was obviously not happy, but I apologised and we have to move on.
"Since Singapore, I've been trying to be really cautious at the starts and it's been frustrating to be involved in an incident in Japan.
"I've sat down and looked at things again with the team - for sure it's still an area we need to improve."