The 72-year-old was admitted to the Albert Einstein Hospital in Sao Paulo on Tuesday.
"I couldn't imagine the Brazilian people would worry that much about me. Thank God I'm well now," the three-time World Cup winner told Globo Esporte.
"I thank all those that prayed for me and I'd like to say that I'll get ready for the World Cup."
Brazil are hosting the World Cup for the second time in 2014.