White Clover is highly attractive to several bee species, including bumble bees and honey bees, so you might want to consider leaving it in the lawn.  If you do wish to eliminate it, besides hand pulling, you can control it  with products containing MCPP and/or triclopyr.  

Here is some detailed information about this plant: https://apps.extension.umn.edu/garden/diagnose/weed/broadleaf/creeping/whiteclover.html

You can apply fertilizer now through the end of October.  If you wish, you can apply one that also controls weeds.  To have the best idea of what nutrients your lawn needs at this time, consider having your soil tested.  See https://turf.umn.edu/news/new-soil-testing-forms-and-prices-umn-soil-lab

Most fertilizers available in retail stores at this time contain appropriate nutrients for your lawn.  For information about lawn fertilizers and how to choose the appropriate type for Minnesota, see https://extension.umn.edu/lawn-care/fertilizing-lawns#types-of-fertilizer-1256813