Depending on what they look like, you may be fine to mow whenever you are ready.
The wasps that are aggressive and likely to sting are those that live in and defend communal nests like yellow jackets. Do you see them all coming and going into one particular spot? Those we'd avoid.
Others are what we would term solitary wasps or mining bees, and they are not aggressive at all and don't sting unless handled/squeezed. They are either pollen eaters, or they eat other insects. Right now there are solitary wasps like scolids, flying low around the lawn surface (kind of a figure 8 pattern). These are females, who use their stinger to imobilize grubs to provision the single hole in the ground she has made so that her offspring have food once they hatch. They do not fly en masse nor do they defend a nest. You can mow right over them.
Here is a page about them, including photos: http://extension.umd.edu/hgic/scoliid-wasps-lawns
If you can get a clearly focused digital photo and attach it to this reply we could help you with identification if needed.