IM ALL BOB

well I had my tires rotated and balanced and about the same day I srtarted hearing a thud thud thud sound at slow speeds.. well I checked over the axles/boots.. and then I looked at the spindle nut and the drive side one seems to have a second Notch on it.. as though something smacked it.. I was wondering if anyone has had this happen to them before and would that cause a thuding sound when the car is in motion? could this have being caused by overtorqueing when rotating my tires? any info or suggestions will be grateful.. I'll probably take it off and get a new one