Boy Trouble

Okay all of you mothers of little boys.....I need help. At least I think I need help...maybe its just a phase or something but what do you do about your son playing with his little schmeckel constantly!! The other day I got him out of the bathtub and was putting lotion on him. He grabbed the lotion, put some on his hands and went to town on his manhood. I kept telling him to stop but by the 3rd or 4th time I said it, I noticed that "it" was at attention. What do you do?
Also, Carter has it out for his sister. I am constantly finding new bruises all over Avery's back and head. He will go out of his way to knock her down or jump on her or throw stuff at her or push her down. Its impossible for her to even walk around him. We've had talks about being nice to her, family home evenings specifically on loving our family members and it just doesnt seem to be getting through to him. Any suggestions would be helpful.