That usually happens because of the wrong size jamb. Older home , out of square , etc. Is that a pre-hung door/jamb combo kit ? I've had this happen many times. I will always make sure it is flush with the drywall on th inside 1st. Then trim down the outside jamb that is possibly sticking out. And /or have to customize the door mouldings around it. If it's just screwed in , you could still fix it. But might be too late or not worth it to you.