If your car tire has a leaky nozzle how do you repair it?

They are usually referred to as a valve stem. If you remove the cap and place your finger over the hole and feel air, you need a tool to remove the core and replace it.

You can get the tool at any auto supply store. If the valve is not leaking from the top

the tire must be removed, because one side of the bead must be broken so that the new stem can be pulled through the rim.