You replaced the cold water nipple on your hot water heater now you have NO water pressure at all?

No pressure anywhere or only hot water faucet? I'm guessing just at the faucets. Very often when you open up the water line rust and sediment will break off and plug the screens on the faucet. Sometimes it lodges in the faucet itself. Most faucets have a screen at the end of the spout that unscrews. I'll bet that solves your problem.