My own daughter sometimes bites herself when she gets frustrated! She is now 22 months and has been doing it for a few months. It is less often now (she talks very well), but she has a temper when she can't do something she wants to do, like zipping up her own jacket etc. However, she doesn't show agression to the other kids, so I ignore it if she hurts herself...she is doing it for attention I guess (my husband tells her not to though). I would be more concerned about the throwing things and hitting others etc. If he throws a toy I would not give him another one...if you throw toys, you don't get to play with them until you have calmed down.