In terms of making friends, yes it will affect you since most of the people on the course will have already developed their friendship groups. Plus you'll miss a big part of uni life such as freshers fair, going out, meeting new people etc etc. Although saying that, you could join societies which will give you a good opportunity to meet new people.
On the studying side of things, first year doesn't count but whatever you learn in the year will be assumed knowledge for your second and third years so it's good to understand what you are being taught.