I understand your issue very well, being a part of the group is cool and nice since you have people around you that you like. I do think though that they probably wont really mind if you wont smoke with them,try to decline in a friendly way if they offer you cigarettes with a small explanation if they wonder. I also had friends back at school who smoked frequently, but they were completely fine for me not smoking with them. They were still very kind to me and accepted me the way i was. Its likely they are the same, just young people enjoying their break between sessions with people they know.
Also, if you buy cigarettes before uni, try to avoid the place where you buy them. Maybe youre connecting the place because you get yourself some food for the lunch break. Maybe go to a bakery or a cafe if its close to you.
Its okay to smoke, but the amount needs to be controllable. I had a case where someone died because of that. Remind yourself to not overdue it, set yourself a limit you wont exceed and stop once you reached it.
GL on your journey :)