I had also faced the similar issue in the recent past. I did lot of research on it and found the solution on it. This is the very common problem with the people getting started.
You need to just kill all the node process and start your npm server and run application with the use of below commands :
Step 1: Run the command as
killall -9 node
For the windows users, need to run:
taskkill /im node.exe
taskkill /f /im node.exe if your process still persists.
Step 2: run the command as
npm start --reset-cache
Step 3: run the command as
react-native run-ios OR
Closing your current Metro Bundler and just restarting by resetting your cache worked for me as below :
npm start -- --reset-cache