My younger boy often bite my elder boy. Whenever they are playing and younger one cant get what he wants he will bite his brother. Both are 15mths+ What can i do to teach him not to bite? Any useful tips to share?

I used my fingers & flicked my lo's cheek since young.. Now lo doesn't bite anyone or put things in de mouth.. Until in childcare where they learn a few gd & bad things.. So far lo only been bitten by other children haha..