A small abscess or small hematoma, or possibly a small cardiac condition. Very likely, a large cough.
A small brain would inject a small amount of gear into a small vein intentionally.
If you've just done it, and you're worried, don't be. But don't even THINK about doing an IV shot of gear. There's no point, and it's extremely dangerous to inject viscous fluids intravenously - especially non-water-based fluids such as oil-based anabolics.
-M