Port 3000 is already in use [nodemon] app crashed - waiting for file changes before starting...

It seems like there is an issue with running your application on port 3000. The error message "Port 3000 is already in use" indicates that there is another process or application currently using that port.

To resolve this issue, you can try the following steps:

1. Stop any other applications or processes that might be using port 3000. You can use the following command in the terminal to check for processes using that port:

   lsof -i :3000

This command will show you the process ID (PID) of the application/process using port 3000. You can then use the `kill` command followed by the PID to stop the process:

   kill <PID>

2. If you are running multiple instances of your application, make sure to stop all of them before starting again.

3. Restart your computer. Sometimes, certain processes might still be running in the background even after stopping them.

Once you have freed up port 3000, you should be able to run your application without any issues.