Both certainly could
Both of these can cause posture, shoulder, back and/or gait
The pilonidal cyst
likely had you sitting in funny ways to keep it from hurting. You might have even been walking funny as a result. Whatever impact fractured your sternum almost certainly affected you shoulder girdle and/or thoracic spin. You should seek out a do skilled in omm to help set you straight.
Answer assisted by David Miller, Medical Student