Swap water the feed for the front washers to rear and rear to front and see if rear washer works.
During cold weather pipe to feed the rear may have frozen, and if you tried to operated the rear washer it may have forced the pipe off a connection.
Also as you suggest might be a blocked jet.
You could also try blowing air down rear feed to clear jet
Maurice
January 2011
howtomendit.com for free repair help, information and advice.
