Technically, you could convert your curves into surface with Birail3+ tool, however, I'd rather believe, you wouldn't wish to go into NURBS modeling tools right now, therefore it would be much more easier for you to use default Nurbs sphere (rotateY: 90°) and transform it's CVs into the shape of the head, where you can use your existing curves as a reference. Then Modify > Convert > NurbsToPolygons and choose the best tessellation method that suits your further plans.
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Maya2019.1 @ Windows10 & GeForce GTX1080Ti
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