I noticed that i have a pea-sized black spot on my thumb and i am not sure what it is. it is slightly raised like a blister, but does not hurt.

Let doctor see it: This one requires an in-person visit to your doctor, to determine what it is. Are you a gardener? Could you have gotten stuck with a thorn previously, or otherwise injured yourself? Do you grow warts? Please let your doctor see your thumb, and go from there.

See a physician.: It is very difficult to diagnose skin lesions without examining the patient my guess is.It is probably a small hematoma which is a collection of blood under the skin.