nothing much. you may stress it. if it's 3 inches tall i would just leave it a few more weeks. if by some mad mistake you meant 3 ft. then it will flower. i'm sure i readd rite.
yes it will flower when it's ready, you will still get some veg growth of about a month. men show sex around 15 days. you could get any where from 3 grams to oz..just depends. I'm doing a 12/12 straight from seed outdoors.
it will flower eventually but it's best to wait till you get staggered branching that's a sign of maturity and that will start flowering... you might get an 1/8 or so but cross your fingers....