With the wiper running see if the wiper arm post sticking out of the wiper cowl is spinning inside the wiper arm. I doubt it will. try to move the wipe manually on the passengers side. You should not be able to move it freely.
I'd say the wiper transmission arm has ether popped off or the wiper transmission itself needs replaced. If there is a problem with the wiper transmission you will need to remove both of the wiper cowls to inspect or replace the transmission.
I'd put my $$$ on the arm on the transmission just popped off.