How can I change a typo in the author affiliation after publication? I am really needing help. There is a typo on my University Name, however  the paper is already published. Is there any way to still change it? The paper has been published on ACM Platform.

I am very concerned about the reputation of my research with this minor typo. I spent a lot of effort to this research and just realize that...
First of all, calm down. This is not as big of a mistake as you think it is. Many if not most published work contains insignificant mistakes such as minor typos. If it would make you feel better, I once had a typo in my own name (I blame autocorrection).

Contact the editor. They are probably going to publish a correction or erratum. If it is already published, they probably won't fix the original published article even if it is online only. (I am not familiar with the ACM Platform.)