Can you get a concussion from a tap on the head?

Depends on how hard: By definition, a concussion is a head injury causing loss of consciousness, loss of memory or a combination of both. If this did not occur, you did not suffer a concussion.

Depends: The effects of concussions can vary and be unpredictable. It depends on the severity of the injury. The symptoms can include headache, dizziness, vision change (blurred vision/ double vision), nausea/vomiting. If your symptoms or headache are severe, or if you have a loss of consciousness, you should get evaluated immediately.