We had a cracked drain and turned off the water to fix it, now the water won't come out the sink. Help!?

maybe the water froze

You actually have two pairs of valves there, one pair under the sink, or "stops" which it sounds like you turned off (maybe to keep other people from running water 'til you got the drain fixed), and the other pair is in the faucet itself on top of the sink.

Tpjp19's suggestion on the aerator is good, but if that doesn't succeed, see if you've got flow through those stop valves under the sink (shut off the house main, put a bucket or bowl below the valve(s), disconnect the water line there that goes up to the sink faucet, have somebody nudge on the house main, and see...). These cheesy valves are notorious for causing problems, including not shutting off or turning on properly. If at fault, take one off the pipe and go get a replacement for one - or both, good time for it - , preferably a "ball valve" stop.

When you shut the water off the rubber washer may have broken and clogged the line.

Shut the main water off and pull the valve handle and see if the washer is intact then turn main on a little and preferably have someone watch and see if water flows.

Not sure why you would have turn off the water to replace the drain but anyways sounds like the valve stem is turning but not the actual core. turn off the water to the house and replace the faulty valve.

You have a plugged aerator screen, unscrew it from the faucet and clean out all the tiny rocks from the screen.