Small dents are not "normal". They may or may not affect performance. Mostly you get pulsating
brakes, the risk of a tire blowoff and the chance the tire may be abraded by the brakes, depending
on how bad the dent is. Also, you may have a structurally compromised wheel since the spoke tension
at that one spot is likely to be incorrect. I once dinged my rear rim on my MTB on a rock. It was a
significant dent, very obvious from 2 or 3 feet away. I rode it that way for 2 weeks with no ill
effects other than an almost useless rear brake. I eventually rebuilt the wheel with a new rim. It's
almost a case of what can you live with, really.