Can you submit your project early if you finish?

Nothing's stopping you but there could be more to add or refine in your game. There's plenty of time before you need to publish, no need to rush. But if you're confident in your game then by all means go for it.

Ok my game will be posted tommorow

Yes, you can submit your game early if you desire. As long as the game is submitted before the timer runs out on the itch.io jam page, you can submit.