Did you start the seed in paper towels first? If yes, don't worry till it's been 3 days you should see something by then. If no, it could be more like 5-6 days. Those would be the late end of things. Depends a lot on temperature.
I would say put the light on a timer now unless you suspect the temps are low then i would leave it on for the heat.
Cheers,
SilverSerf