Schumacher was taken to hopsital after a crash at the race track in the Spanish city of Cartagena on Wednesday, but was later discharged and flew home to his family who live near Lake Geneva.
"Thanks for the many 'Get Well Soon' wishes, but I am fine today," Schumacher wrote on his website on Thursday. "I am not perhaps as articulate as usual, but all checks show that everything is ok."
False reports in the Spanish media on Wednesday, citing sources at the track, had claimed the 40-year-old had multiple injuries and was left unconscious after the accident.
But Schumacher's spokeswoman Sabine Kehm told German sports agency SID her client took no more than a heavy tumble and may have been briefly knocked unconscious after his head hit the tarmac.
Schumacher has been involved in motorcyle racing since he retired from Formula One at the end of the 2006 season and has competed in the German Motorcycle Championships (IDM).
This is the first time he has been injured while racing.