You have breadcrumb feature turned on where it keeps a record of your routes And travels?
NAVI MENU button on DIS ---> SETTINGS ---> MAP DISPLAY ---> SHOW TRACKING - uncheck the check box.
If you move your DIS knob when Show Tracking is selected you can reset all tracking and blue dots will disappear. I just did that because I was also wondering what those were.
I thought the same thing at first. (What the heck are the annoying breadcrumb type dots that seem to be showing my path?)
Then once I figured out what feature it was, I thought how stupid, and I turned the tracking feature off. AND THEN, shortly after I turned it off, I had an occasion where it would have been helpful to easily refer back to what route I used earlier in the day, without taking a few extra mins to enter a new location on my (barely usable) navigation software. That's when I realized the tracking feature could be useful, albeit occasionally.
For example, if you're in an unfamiliar area across town and then you need to navigate elsewhere (ie the grocery store) but then you want to get back to your first location but don't have it entered as a destination on your navi--it's actually useful. Now that I know that, I leave it on now.
The tracking feature basically just gives one more data point (literally) to have available for finding your way around if needed, without having to stop and enter a new destination.