I know a little about this.
There is no difference between getting your bell rung, seeing stars, light dimmers, or a concussion: they are all one and the same.
If you experience any alteration in mental status as a result of a blow to the head - nausea, dizziness, hearing changes, flashes of light, headaches - even for a couple of seconds or so, you have sustained a concussion. You
do not have to get knocked out to have a concussion, but
all knockdowns and knockouts are concussions.
The best thing you can do is
STOP TRAINING RIGHT AWAY and take a break from getting hit in the head for a bit. Get checked out by a medical professional before you return to training. I am not trying to scare you, but getting another concussion when you have not recovered from the first one can disable or even kill you.
And even after you've recovered, concussions add up. The more of them you get, the longer the symptoms stay with you, and the longer it takes for you to recover from them. If you're particularly unlucky, you may never recover if you sustain enough concussions.
I know that combat athletes are trained to push through pain and injury, but a concussion is
not something you want to push through. I am speaking from personal experience.
If in doubt, sit it out.
Jeff Joslin has
an excellent blog post on concussions from a combat sport athlete's perspective.
The current medical thinking on concussions is summarized in the
Zurich consensus statement on concussions in sport. The SCAT2 and Pocket SCAT2 in the appendix of the document provide professionals and non-professionals respectively with tools to determine if an athlete has sustained a concussion.
You can find clear and reliable information on concussions at the
University of Buffalo Concussion Clinic Web site. One of the doctors at the clinic has a pretty
informative paper on what happens when you get a concussion.
I'm a little on the fence about this, but it may also be helpful for contact sport athletes to get baseline neuropsychological tests like
ImPACT or
Vital Signs done before they're concussed, to help manage their concussions once they get them and determine readiness to return to play.