What do you have to do after seeing colress in route 22 in Pokemon black 2?

After encountering Colress on Route 22 in Pokémon Black 2, you should head to the nearby Pokémon League. Colress will mention his interest in powerful Pokémon, leading you to challenge the Elite Four and the Champion. Completing this challenge is essential to progressing in the game's storyline and ultimately facing Team Plasma's plans.