If a crankshaft pulley is loose it will cause rough idle, loud noises, ticking noises, banging noises, engine vibration, potential damage to other engine components including the power steering pump and alternator and possibly the transmission.
A loose crankshaft pulley can also cause the serpentine belt or engine belt to slip off and even shred.
Crankshaft pulleys are bolted onto the crankshaft and if it's lose it will come off eventually when the bolts holding it on come completely out.
So you should also get the loose crankshaft pulley fixed before driving any further or it will lead to other issues and leave you stranded.
The crankshaft pulley should not turn freely or spin freely by hand when the engine is off.
The crankshaft pulley should be able to rotate but should also be difficult to turn, especially by hand.
You should be able to use a socket and ratchet to turn the crankshaft pulley and it the crankshaft pulley does not rotate at all then there's an issue with the engine.
If the crankshaft pulley rotates freely then there's an issue with the engine.
The crankshaft pulley is connected to the crankshaft which also drives the pistons and rods in the engine and so it should be difficult to turn.
The crankshaft pulley also drives other engine components such as the power steering pump, alternator and water pump through the serpentine belt.
When the engine is running, the crankshaft pulley also rotates and this same rotation is transferred to these other accessories.
The crankshaft pulley should spin easily when the engine is running but not when the engine is off.
If the crankshaft pulley cannot be turned very easily or at all it could mean the engine is seized or something is locked up in the engine or the pulley is misaligned or there are worn components.
Other pulleys such as the water pump pulley, alternator pulley, and power steering pump pulley as well as idler and tension pulleys should be able to turn freely when the belt is not in place.