Smoking

A week ago I broke up with my bf of 2.5 years. He was controlling and not very respectful, and we had different plans for our future, but getting over him has been very painful and emotional. I was starting to feel okay without him, but today a mutual friend of ours told me that he offered my ex some cigarettes and he accepted them. It just tore me apart, the thought of him doing that to himself makes me want to break down crying. I feel so helpless knowing that I can’t help my ex anymore or tell him that it’s wrong. I told our friend not to give him anymore cigarettes and keep him from buying any if he’s able to. He tells me he doubts my ex will get addicted but I don’t believe it at all. I feel so horrible, and like it’s partly my fault because I was the only thing that made him happy. What should I do? :(