Is it obligatory to inform one's husband about having lied to him regarding a dream vision, claiming it was to name "Hanin" for repentance, and how can one atone for this sin?

Naming is the father's right. What you did by claiming a vision you did not have is forbidden, and you must repent and seek forgiveness. If your husband agreed to the name because of the alleged vision, you must inform him of the truth so he can change the name if he wishes, provided that no harm or corruption results from it.