Is this a custom field? As JIRA doesn't provide a system field "created by" system field. If its a custom field then you can remove the field from the "edit" screen in order to make sure it's only filled at the time of creation.
If you are talking about "reporter" field then you can follow the approach as suggested by @Udo Brand
Atlassian Summit is an excellent opportunity for in-person support, training, and networking.Learn more
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG