If it's oil paint you can sand it down, especially while it's still fresh. If it's acrylic/latex that won't work so well. It tends to scratch rather than wear, like sanding rubber. If it were me I'd live with it, but given that you already stripped the old paint (!) it sounds like this is a special door.
If you want a really nice finish next time, prime with oil underbody primer and paint with oil or acrylic alkyd paint. Another trick is to not use semi-gloss. The less the gloss, the more forgiving of imperfections.
| | I painted a door with semigloss paint after stripping and sanding both sides | smooth, then priming. One newly painted side looks good and smooth, but the | other side looks really bumpy. I used the same painting technique for both | sides - rolling the paint on and quickly laying it down with a high quality | brush. | | I am trying to avoid restripping the bad side or spending a lot of time | sanding the paint down. Is there some way to fill in the "valleys" without | going to a lot of trouble? | | Any advice appreciated! |