There is a nut under the black cap where the wiper arm pivots. That probably came loose and needs to be tightened. Remove the cap it just pops off then get the corredt size socket or wrench and tighten it. Make sure the wipers are in the off position when you shut off the car so when you tighten it, it will be where it belongs. There may be a small line on the windsheild where the wiper sits at rest with wipers off.