I Accidentally Hit My Head Two Days Ago. I Felt

I accidentally hit my head two days ago. I felt a little in a fog and slowly developed a minor headache and neck ache. I was also quite tired, but that may have been because I was so nervous that I might have a concussion. I've been worried that I may have suffered a concussion, but I'm no longer in a fog and my cognitive abilities are normal. I have no amnesia at all. I have had a slight headache, but it comes and goes. I have been resting a lot. I'm not sure if I have a concussion. What do you think? If I do have a concussion, I am quite nervous about accidentally suffering Second Impact Syndrome.