The error says that, the url that you are using for the Image is not from a trusted hostname(domain). You just need to add that hostname or domain inside your next.config.js file. Follow the following steps :

1. Create a next.config.js file inside your root directory.
2. Add the following code inside your next.config.js file.

module.exports = {
  images: {
    domains: ['assets.example.com'],
  },
}

This must solve your problem. For more details you can read more on this page : next.config.js