There is nothing to worry about. Pencils are made of graphite which is carbon. Since your body is also made of carbon you cannot be toxic to it. Yes, you will get a "tattoo" from the graphite but mine has been there for over 40 years and there is no problem related to it. I also have one in the roof of my mouth (don't ask!) but it's again no problem!
I have one in my back.Im 10 Now i was at school and my friend poked me in the back and its a black spot.and now im filling like my lungs r cloged what should i do.im scared
Most unlikely that a sharp object would leave behind ,sufficient lead to cause symptoms many years later.Basophilic stippling of the blood cells,and gum lesions with bluish discoloration would help in arriving at a diagnosis,apart from blood lead levels.