Dont let it get to a situation where he can get away with it this young. take him out on a long line and re-install the NO command, nevermind stop whistle. Just enjoy him being a baby, stick to basics and get him well socialised/stock proof etc.
Biggest thing to concentrate on is NO and recall. Dont be afraid to give him a shake if he cocks up as he will, hes young and daft, just train for success the now, more serious stuff can be next year.