I don't think you said how long it's been. But, the most critical thing you can do after a concussion is total, absolute rest! That includes thinking. Try to get as much quiet time as possible.

Your brain is going through a process of reversing some chemical changes that happened right after you hit your head. This process can take a few weeks. Basically your brain needs glucose to repair itself, but your blood vessels aren't allowing as much blood to your brain as they normally would. So physical and cognitive rest are so important.

Wish someone had told me this. I went about my regular life. I'm pretty sure this is why I'm having issues 2 months out. The last of my symptoms, (vertigo, dizziness) didn't start happening until almost 2 weeks after hitting my head.

Other things you can do:
Eat lots of protein
Eat anti-inflammatory foods like turmeric and resveratrol (grapes)
Take an omega 3 supplement, (fish oil)
You could also consider taking creatine.

This is all stuff I learned after it was essentially too late to get the most benefit.

I would wait 3 weeks before going back to Judo. Make sure to work with a doctor. I know it probably seems like a really long time, but I'm 7 weeks out and dying to get back on my bike. I was training 15 hours a week. It will probably be another month or two before I can start again. That's a lot longer than 3 weeks.