Q: i brought a new iphone today and the shop man put a nano sim card in, how long does it take for the sim card to work is it 24 hours or up to 24 hours? is it normal for it 2 say no service?

Have another phone you can use to call your carrier? If so, call them & they should be able to activate the sim over the phone.

SIM's should connect nearly instantly, otherwise reach out to your carrier to activate it.

Are you outside of the SIM's home country? If so, not all carriers support roaming.

It started to work within 15 minutes after receiving the nano sim for me.

Well, if you can find a way to call your carrier, as I originally stated, you can fix this right away.