Hey there, Bj_cairns!
Welcome to Apple Support Communities! If we understand correctly, you're running into an issue with accessing your Hotmail email account on your iPhone. We also understand this started happening after you set up a verification code for Hotmail on your laptop. We can understand wanting to find out how to correct this issue. We will do all we can to help get you pointed in the right direction.
What type of iPhone do you use? Which version of the iOS software do you currently have installed on your iPhone? You can find this in Settings > General > About.
Do you run into any issues when you attempt to access the email account from the laptop? Or does that still work without a problem?
Is it possible that you have a specific password set up for when you access Hotmail using the Hotmail app, Mail app, or any other app you can link to? If you're unsure, here's how to check: Using app-specific passwords. If not, or if the app-specific password was set through Hotmail directly, you'll want to reach out to Hotmail for further assistance.
Take care!