Can you put a 25t chainwheel with a 13t freewheel on a bmx bike?

[MattSetsHisFriendsOnFire.]

I don't like the way a 36t chainwheel looks on my Stolen Pinch 2010. Can I just change the chainwheel without changing the freewheel? I've heard that if you want to change the chainwheel you have to change the freewheel to a 25t/9t combination.
Thank you for your help.