I agree with carver, use a small spoon or something similar and scoop it back into the container. Any that you can't get up that way, sweep it up and put it in your flower bed. Powder costs too much just to throw away if you can safely salvage it.
The ONLY bad side effect I've ever experienced was getting some lint mixed in the powder. That jammed my powder measure. But that is it. I found a cheap kitchen strainer from the grocery or basic house hold goods store will take out most of the impurities.
The salvaged powder loaded to the same data and shot the same way it always did. A minor amount of dust didn't seem to alter he burning rate.
I'm too cheap - uh - thrifty to throw out $20 worth of much anything if I can avoid it.