For meningitis, the classic test is to tilt you head down and try to touch your chin to your chest. If you can't, you have inflammation that is a problem. If icing it resolves it, it is likely a neck injury. If not, get a doctor to check you out. If you can touch your chin to your chest, it is likely just neck inflammation.

A meningitis vaccination is not 100%. They are grossly oversold as complete prevention. They just reduce the risk.

You should be icing your neck regularly. I can't think of how someone can get a concussion without also traumatizing their neck.

I doubt you have meningitis.

You probably became to active from feeling better and aggravated your neck. It is a vicious cycle. Just because you feel better does not mean you are ready to return to full activity.