Yes, my girl also like to hit her head many times when she was 11 months especially when she upset and frustate..but she stop do that when around 14-15 months.. i always say do not hurt yourself and pick some toys for her to hold or distract her with toys/games/snack...perhaps it works for your boy..
maybe distract him with something else. example toy or music coz they are easily distracted at that age. !