Like bubster said you probably could have fixed that without repainting. I would have used 1000 to start and ended with 2000. If you are carefull and use warm SOAPY water you can get the sag out and then rub it back slick. It will look even better than it would have if you had not needed to fix it...color sanding is what gives em that mirror look not just a high gloss. I almost only use base/clear but you can also color sand acrylic as long as it doesn't have metalic in it. If you color sand single stage paint with metalic it looks blotchy because some of the metalic gets removed from any high spots.
The soapy water helps the paper glide across the still soft paint easier and keeps it from scratching.
If it sags on you again close to the wheel well, try and run it off the edge.
I agree with bubster about the ring in the paint. I have had that happen. Always do the whole panel or break at a molding or body line...unless using b/c c/c then you can color just the spot if you want and then clear the entire panel.
JMO as I am not a profesional, but I have painted a bunch of em.