Years ago, i had a back tooth extracted. the bitso amalgam filling was trapped in the socket. now, i have bad pain in thearea. could this cause infection years later?

Not likely: If your extraction was years ago, the pain is likely associated with something else. I recommend seeing a dentist for an exam so that you can be certain of the cause of your pain.

Probably not: Typically the amalgam will leave a dark tatoo visibly but the material is inert and I have never seen this inflame the nerve, but there is always a first time. I would see your oral surgeon to evaluate if the area needs to be cleaned out.

Absolutely: Any foreign material may act as a nidus for infection depending on many factors including the integrity of the surrounding hard and soft tissues.