I've had a saltwater tank for a few weeks now, cycled, tested with damsels, levels checked etc.

Yesterday I added a small blue regal tang into the tank with it's other tankmates (clown, yellow tang, firefish, cardinal, cleaner shrimp). It seems to be doing fine, except that occasionally it repeatedly scrapes it's side against a rock over and over for a few minutes. I don't see any white spots are other markings on it the suggest a sickly symptom. I'm new to this so I don't know if this behavior is normal for this fish or if it's a sign of ICH or some other sickness. Any thoughts?

firstly,what's the size of yr tank? tang fishes do need a large tank as they are very robust swimmers.if the tank is too small,they do get stressed out.
if yr tank is of adequate size,then it cud just be aclimatizing itself to yr water parameters. monitor it closely to see if "ich" surfaces. if it is swimming and feeding well,it shud be able to resist it. take it out for treatment when it show signs of heavy breathing or lethargis.