22 years old and experiencing piercing chest pain near the left brest, for <1 minute. not fluently . what can this be, i'm fairly healthy. ?

Few things: Might be costochondritis- an inflammation of intercostal nerve, especially if it increases on inspiration, can be pleurisy especially if you had recent cold or flu. It might be cardiac, although unlikely at your age unless family history of cardiac problems at early age, or personal history of drug abuse. Can be breast cyst or mass, can be muscular pain. Etc.

Musculoskeletal: While it could be anything! the most likely with sharp, brief, mild is not cardiac. Occasionally lung or pleural, issues will present like this. Hope, it has resolved by now. If in the breast itself, may be cyst or mastitis. Feel / examine and then see your primary care.