You may need to remove the items stored under the kitchen faucets black. The nut is underneath the sink and may require removing a protective layer. Be sure to put back the sink cap and nut after you're done. It's better to call a plumber if the problem persists. If you're not confident enough to tackle a DIY project, call a plumber. A loose kitchen faucet can lead to a leaky water supply if you don't have the proper tools.