Round up where it was not intended

A couple of weeks ago we had a beautiful crop of dandelions around the based of our trees.  I decided that we needed to spot spray with a backpack to kill them.  When the tank was mixed, some non-selective material was either still in the tank or left in the line.  We should have placed some rinse in the tank and sprayed it out to insure we had the proper material going down over the top of our turf that we wanted to keep. Hate making mistakes. Will insure proper material handling in the future.