Soft Spot Swollen

Hey, mom as. I'm really concerned about my little one. His soft spot is a little swollen on the top of his head. It usually is sunken in a bit. He is almost 5 months old. I canny look at it and tell but when I run my hand over his head it is a bump. It usually isn't like this. He fell off our bed the the night before last onto a pillow. I called the doctor but they said not to worry just look for signs. Well, the soft spot is still like that. Should I take him to the ER? I'm really concerned. Has anyone ever had this happen?