Fermentation can start anywhere from a few hours up to 72 hours from when yu pitch the yeast. Many factors will influence that. The fact that it started so quick is actually a good sign, be proud, your yeasties are making beer.
It will not hurt it to let it sit there. I routinely let mine sit for 3 - 5 weeks.
Welcome to the hobby, and the site. Plenty of great info to be found around here.