From personal experience I've found it better to air on the of caution for the first 3 weeks post hitting my head. Symptoms from concussions can take a few days/weeks to appear and your brain is often working harder than usual after a big bump even if you do not have defined symptoms. My last bout of PCS, I hit my head but felt mostly fine, so continued onto so big sporting events I had planned. Then a week or two after had sympoms of fatigue and concentration seep in with vengeance.