What Do I Do??

Last year I broke up with my boyfriend because my best friend had been telling me he had been doing things behind my back. This year, I found out the truth and it turned out my ex did not actually do any of the things my best friend said he did. I want to show my ex that I’m sorry for what I did but at the same time there’s still my best friend, who has supported me for almost 2 years now. I still have feelings for my ex but I’m not sure what I should do. Can anyone help me??