Bed ramming into extruder nozzle

I took apart the extruder in order to remove a clog and I just finished reassembling the extruder.  While the plastic is now extruding fine, the calibration on the z-axis is off and the bed touches the nozzle when z = 7mm, making the nozzle ram into the print head at the start of any print.  I have tried correcting for this in the Slic3r settings, but the print bed continues to rise into the nozzle both at the start of a print and when moving to the home position.  I would really appreciate help as this is my first experience with a 3d printer.  Thanks!