You have a short of SRN trace with this one somewhere in PCB. KiCAD trying to avoid such shorts, but sometimes he can't help it (for example - when you change schematic and some refdes or pins changed they nets, when you update PCB, and get what you got)
KiCAD do not complain about shorts (as they created), but it will complain in DRC run (if you will check 'test for parity between PCB and schematic')