What does it mean for a male colleague to invite me to dinner to see cherry blossoms?

It's hard to judge what he means to you now, because as a colleague, you helped him and he really should invite you to dinner, but if you refuse him, he can not invite you to dinner, but if he likes you, he will take this opportunity to get along with you alone. If he invites you to dinner without any other words or actions, then he is just thanking you. If he shows more concern and care for you than gratitude in the process of inviting you to dinner,