To make sure that the changes are in production, you need to add the components to an outbound change set and deploy it to production. A change set is a tool that allows you to send customizations from one Salesforce org to another. A change set can contain components such as objects, fields, profiles, permission sets, workflows, and more. You can use change sets to migrate changes from a sandbox org to a production org or between two sandbox orgs that are affiliated with the same production org. In this case, you need to add the master-detail field and all the affected profiles to an outbound change set in your sandbox org and then deploy it to your production org. References: https://help.salesforce.com/s/articleView?id=sf.changesets.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.changesets_components_field.htm&type=5