My 15 month

My son climbed on the couch and stood up at the edge of the couch & fell back onto the floor. He hit his head.

What should I do?? He cried for 2-3 minutes. Now he’s laying down on blankets.

Do I keep my eye on him? What should I look out for and for how long? Over night? I know I should probably be asking a nurse but I thought I’d try here first for advice!