If you used a base/clear on the car, you can wet sand with 600 grit to drop the elevation of the bumps...........clean it foo well, and look closely for surface "pits" against the glare of the light......resand those areas lightly, and prep for another clear coat.
If you used one stage, either your reducer was too fast, or your ratio was too thick..........a zahn cup is the trick for consistency (it "times" the paint as it runs through a small cup, so your ratio is dead on), due to temp variances and paint brand inconsistencies.................If you have just a color coat, wet sand with 600 to smooth it out (use a medium-foam block for your paper....it won't "cut" from the edges)...........Follow that up with another color coat.........ONE coat........after a complete flash, check the surface..........You may be ready for a compound buff as-is.
If you have an aggravated case of orange peel, you will most likely have to recoat the surface..........Just a sand and buff will look better, BUT you won't get rid of all of the low areas as well as with a recoat and buff....AND, as previously pointed out by other members, you should use an 800 grit minimum for this.....600 is only for recoats.....800 to 1000 for buff-only projects.
New clear coats are thicker than in the past, and VERY forgiving in these circumstances........I wouldn't worry too much if it's base clear. You'll be OK.
:thumblef::thumblef: