as lankeela said, sounds like normal doggie behaviour. just squeek when he nips you and walk away, ignore him for 5 mins until he calms down and then carry on as normal. i'm sure your doing fine, border collies are natural herders and your westie will tell him off and put him in his place. it's natural but do feed them seperately and like lankeela said buy a pen or crate for the border to seperate them and give him his own space. you don't say where you live but i'm a dog trainer and puppy socialiser so if you need more advice,.....,,..,.,...,,,,