I am not totally certain if I understand your question. However, since you say you extruded the shape, I'll assume it is a sleeve or something similar.
The would be sharp, and to round it off. I prefer to let the model shape to the rounding...it keeps things simple and gives very good results.
- Be sure it is a NURB. You can convert from B-Spline if you need.
- Use Edit/AddPoint to add two or three rows of points around the end of edge.
- Use Edit/SelectRow to grab the last row of points.
- Use Edit/CenterToVerticies to make the center of surface in the middle of the points.
- Scale or move the Tagged points as needed to get the outside rows to bend the edge inside like the lip of a trumpet horn.
This gives a nice smooth edge and there is not continuity or texturing issues from having multiple surface.
Sorry, if this is not what you need. This works for polymeshes as well, but instead of adding rows you'll have to slice polygons near the edges.
Hope this helps,
Urp