Are you using Pipelines as Code via YAML Config Repositories - and this is what you are talking about?
Assuming so, unless you've turned off auto updating for the underlying repository, by default they should update within a minute. Admins can review the configuration at Admin > Config Repositories.
If the repo and pipeline you changed is updated on the config repositories view but you still don't see it on your dashboard, you might want to check that you have at least permissions for the pipeline group (if adding a new pipeline), that your dashboard view is not filtering any new pipeline and if you are filtering pipelines you default it to include newly created pipelines in the view.