Just had a concussion, i think?

last night i was in a fight and hit my head on the concrete and i couldnt remember anything that happened and i was unconscious for about 5 - 10 seconds, then i remembered getting up with my friends and i dont remember another 20 minutes of us doing anything but they said we walked up the road and i was all fine but after the 20 minutes passed i didnt remember any of it but now im back to normal i guess this happened last night about 8 hours ago and i stayed up all night with my friend because we were told not to go to sleep with a concussion i didnt see a doctor but is this serious? when i bend over or make my head lower than my body i get very dizzy, can i go to sleep now?