Is the warrant nation wide or only in the state the infraction occurred?

The warrant will typically appear nationwide. Therefore, if you are stopped by police in any state it is likely that they will see the open warrant. You can then be picked up and held on a fugitive from justice charge until the arresting jurisdiction contacts the original jurisdiction to see if they are interested in extraditing you (coming to get you and return you to the original state). Chances are that they will not come to get you for a 1st offense OUI. However, even after you are released the warrant remains open and you may be subject to the same process the next time a police officer runs your license or name. You really should get the warrant resolved on your own terms or else it will of course come at the very worst time for you when the police happen to encounter you.