Been at uni for 4 years now and the first day of class is always the worst. I always stutter my way through it, and then after class I would always go up to the professor and let them know about my stutter. I would recomend during your next class you do that, just to introduce yourself again and to let them know your reason for not participating much in class discussions. Every professor ive had has been super understanding and accomendating, especially when it comes to presentaitons and timed video recordings. And as for the social aspect of it, you'll get there. I was in a really bad place freshman year, and because of that I didnt go out and socialize that much. But since then I've made some really good friends and had a great social life in despite of my stutter. Join a club, particiapte in campus events, try to engage in class discussions with those next to you. You'll find that thats a really good way to make some friends amongst a sea of strangers. You've got this!