Should I be worried after he hit his head?

Last night, my 2 year old son was playing around being super rousy as usual. I went to sit at our counter chairs, and he goes underneath it (his head barely reaches the top by an inch) and all of a sudden theres a loud BUMP, as he tried to jump up and he ends up hitting the top of his head on the marble counter.. i thought nothing of it because he cried for not even 10 seconds, rubbed his head, and went back to playing around and running and acting like a normal toddler. We were awake for about 2 more hours and during that time I still kind of kept an eye on him, just in case, but he was acting perfectly normal. No bump developed or anything.

I woke up with my husband about an hour ago, and i felt my son and he seems to have a high fever. Can this happen because of that hit on his head or can it just be a virus or something? The hit happened about 9 hours ago. tried to wake him up and he was fussy and started saying something and so i laid him back down because i know that's a good sign.

Am i worrying for no reason? I just wanna be able to go back to sleep knowing he's okay.. he's laying in bed with me right now so i can keep checking him but i know brain injuries are sneaky..