By "potato bugs" do you mean the wee Pill Bugs or Sow bugs, those land dwelling cousins of crawfish and lobster? They are harmless although greatly beneficial because they eat dead vegetation making larger chunks into smaller chunks that the bacteria can more easily work on. They are more beneficial than harmfull and will not poison your dog, unless the dog ate a ton of them.

Here is a link that might be useful: All about Pill Bugs