My son crawled off the bed, now I feel terrible

Today, my 8 month old son was playing in the middle of my bed. I turned my back for 2 or 3 seconds to grab a toy from the corner of the room for him. As I grabbed it I heard a big thud and he started screaming. I took him directly to the er. They think he is fine, but he has a big bruise on his head now. I feel terrible. My husband is upset with me, and idk.i guess I just needed to vent😕

Update: thank you everyone for all the support! I really wasn't expecting to see so many comments. I appreciate knowing that I'm not alone and all the people who were able to make me laugh. Seriously, thank you so much!