The nozzle(s) need to be removed with the proper nozzle removal tool and cleaned by placing it in the pool water and pushing it up and down several times.   While you are doing this you also should run the system without the nozzle to clean out the plumbing of the circuit the stuck nozzle(s) were in.  If the nozzle(s) still sticks it may need to be replaced. You may need to disassemble the nozzle to fully clean it. Nozzles have a life time warranty to the original pool owner.