My DS is in reception and 4, ive noticed he has been biting his nails over the last few months and it seems to have gotten progressively worse, he's bitten all his nails right down as well as all the skin. He seemed to do this while he is worried but it's become a bit of a habit and im not sure he even notices he's doing it. He also picks his nose out of habit too. We've tried the stuff that you paint on their nails to try to stop it but doesn't seem to make a difference, any advice? His dad also bites his nails but he's trying to stop too.