What usually causes this is. When you put a pin into your muscle you pass through a series of veins and capillaries. After you have pushed the gear into the area and remove the pin the gear doesn's stay in that spot completely.
YOu have probably had the oil come to the surface a time or to. However the oil is trying to find a way out and some of it gets absorbed into the small veins and capillaries you have passed through.
hence the taste.