Could have I gotten a concussion?

Yes, go see a doctor or urgent care clinic. Headaches, nausea and sleepiness can all be signs of a concussion. It's probably a mild one, but you should get it checked out anyway. I don't want to scare you because you are probably fine, but there have been very, very rare occasions when people have hit their head, felt OK, but then had severe reactions and even died several hours or a couple days later.