I have 'swan neck deformity' in three of my fingers as a result of having Psoriatic Arthritis; the inflammation affected the middle (PIP) joints and ligaments. (causing hyper-extension of the PIP joints which ultimately leads to the deformity).
Swan neck deformity can also be caused by injury to the hand.
If you are concerned about your fingers then it might be advisable to speak to your doctor again about it..and perhaps ask to be referred to a hand specialist.
good luck with this Steve.