I hope you're okay! It sounds like you decided you were okay to work, but I learned from experience you can't really trust your initial judgment post-crash. I felt great right after mine, and even the next day, then POW, a severe migraine, which blind-sided me. Even though I went down pretty easy, I felt the effects for a couple of weeks. Take it easy. Your work-mates will understand, and if they don't, they don't deserve you.