Toddler falling + hitting head

I'm a FTM to a BUSY 2 year old. Like, he does not stop moving from the minute he wakes up until he goes to sleep at night. I totally understand he's going to bump his head from time to time and try to mitigate it while letting him get the movement he needs but I'm still so nervous about it. Yesterday at the playground he fell (from standing, not an elevated surface) and knocked the back of his head on a hard concrete surface. This is probably only the 2nd time it's happened, so it's not an everyday occurrence or anything. He recovered fast and I watched him for any signs of concussion. Parents with more experience: do I need to relax!? My husband thinks it's just a normal part of childhood and I'm always so distraught when it happens. Thanks in advance!