If you are living in Maastricht or surroundings you need a family doctor(in Dutch 'huisarts')which you can call upon if necessary. Register with a doctor in your neighbourhood as soon as you can.
Check http://www.hapmaastricht.nl/en/affiliated-GPs to find a family doctor in your neighbourhood.
More info about the Dutch healthcare system in the movie below:
IN CASE OF AN EMERGENCY
Outside office hours you can contact the Huisartsenpost Maastricht en Heuvelland (always call before you visit):