I had really cool idea for game last week, i have never build a prototype or made art for it. It's just idea. 

Can i make game for this jam around it? I am asking because the rules says that all work on game must be done in time of jam

I definitely wouldn't worry about this. I don't think anyone even has the ability to police the genesis date of an idea.

As long as it fits the themes, I'd chalk it up to a happy coincidence that they match.