He fell down the stairs

So today was my boys 1 year dr visit and tears were shed. Parents and child. His dr told me I have been giving him the wrong size Tylenol for his teething(I was giving him newborn size) since his got 4 molars cutting. I gave him his meds and he took a nap. He woke while I was busy changing our baby gate upstairs because he somehow knew how to climb over them. He never fell, he would get stuck on top of the gate. Anyway I'm busy changing the gate and I look away to pick up the gate and in that 2 second glance he was rolling down the stairs!!! My heart just sank and I ran after him. I almost fell on top of him while trying to grab his tiny legs. He hit the downstairs gate with a big bang on his front. He only cried for a minute at most. I've never been so scared in my life. We went to his dr and she said his fine. But dear god I feel sooo bad. Poor guy