Welcome to Health care magic. 1. The history suggest that its infective collection in the axillary region with recurrent aetiology. 2.In this case the treatment will be a small incision and drainage with good post procedure followup dressings ( with medical personnel ) 3.If you are draining with safety pin it will never get healed and it will reoccur - as you are causing the infection ( though you are saying its sterile) 4.Maintain local hygiene, clean with antiseptic liquid, do not compress or scratch the area - it will only delay the healing process. 5.What should you do? get an incision and drainage of the fluid followed by a antibiotic course and good care of wound. 6. Avoid clothing that cause friction / irritation to the area. Good luck. Hope it helps you. Wish you a good health. Anything to ask ? do not hesitate. Thank you.