Little green dot on the skin on the arm. it does do anything nor does it hurt. it's been there for three years. it looks like it was made by a pen.

Skin pigment: There is a condition called carbon tattoo resulting from lead becoming embedded under the skin from pencils or road debris for example . Any spot that is changing or evolving should be examined by a dermatologist to rule out skin cancer.

Dx uncertain: This can't be diagnosed with the information that is available. A history, physical examination & other studies may be needed to determine cause/causes. Once accurately assessed a treatment plan can be developed.