micrograms, which is 1/1000 of a milligram. No amount of lead is considered safe, but you would need to eat allllottttttt of this chocolate before it would get to a level that, for example, a doctor would be concerned about. Ars Technica has a good write up about the CR report

Not that I’m trying to shill for Big Chocolate. When I saw the report, I definitely made a conscious effort to cut back to once a month or less.

Your local health department can probably test the tick for disease if you still have it. (At least mine does in my state). If not, there is pretty good success with early treatment: https://www.cdc.gov/ticks/pdfs/FS_TickBite.pdf