Serina was excused from school because of the incident. Nicholas has covered it up with random excuses and fortunately, the teachers believed the excuse after seeing the medical examination result of that he sent in her behalf. Some students felt relieved that Serina and Nicholas won't be around Paris but it was different for Lambert.
He was used to hanging around with Serina, studying with her, eating with her and looking around the city with her. He didn't have any other true friends except her. With her being absent, Lambert was lonely and was often seen around campus alone. He didn't join other students and he didn't initiate making friends as well.
He just thought that he was going back to square one when he was still looking nerdy and alone.