agreed. You just nicked a vein. No need to panic.
Although, I disagree that you likely lost oil. Blood and oil don't really mix, since blood is essentially water. The oil is thicker. I think it more likely that the oil you just injected is creating pressure, pushing the blood out.
One way to tell: the blood will dry quickly and feel sticky. Oil won't dry at all and will feel oily (imagine that) between your fingers. But I suspect that the oil you lose is minimal.
Pull your needly out more slowly and you'll minimize the issue. Also you can "Z-track" or pull flesh to the side before you inject, when the skin slides back into place you won't have a consistent track for the blood to leak through.