I my experience (Let me start by saying I'm nowhere near a carbon expert) if you do the tap test and make sure there's no separation, bubbling, etc, it should be ok. So, tap with your finger or a penny up and down that steerer and if there's any 'different' sound specifically on or around that line, there could be an issue. Inspect for any separation or bubbling as well. I had a nasty fall once that knocked my rear wheel out of alignment and I rode for a little bit with it rubbing on my frame.. wore a nice little spot out, too.. But according to a carbon expert, there was nothing to worry about, just superficial. What you don't want is separation or delamination or a crack/hole.

There's a fella or two on these forums that work with carbon that can probably give better information, but hopefully this helps anyways.