hi. noted history of painful lump over the shoulder area. based from your description, it may be a cystic formation (sebaceous or keratinous type). other lesion types (such as abscess) must also be ruled-out. it is best if you consult with a doctor, preferably a general surgeon, for physical examination and clinical evaluation. medical (proper antibiotic regimen) and surgical (if indications are found) management will be directed accordingly. avoidance of manipulation of the affected area and maintenance of good hygiene are also advised. hope this helps. good day!! ~dr.kaye