I completely understand. When my daughter was about the same age, I was visiting my moms and my baby was on her bed napping. I put pillows around her so she would not fall off the bed. Well she woke and I did not hear her, she managed to climb over the pillows and fell off my mom's high bed hitting her head on the bedside table on the way down. I cried right along with her and felt terrible. She is now 12, stays on the honor roll and has been nothing but pure joy. Though she has asthma, has broken her arm, strained a foot enough for a boot for 2 months, got metal in her eye, in a minor car accident with her grandfather, in a car accident with me on the tollway 2 years ago, and numerous other minor injuries, she is fine and I just know whatever the next sport or activity is, there is a chance of injury.
Like the others said, your sweet baby is probably fine but if you need that reassurance, call the doc. Most babies fall off a bed, sofa or something. Good luck and enjoy him.