Boyfriend jealous of classmate, we three stuck in a project together

Advice needed, please help.
So, I'm a female and have boyfriend, who studies in the same course at Uni as me.
When we started dating, a guy who was a friend, who also studies at the same Uni on the same course, said we was into me. I said I didn't have any romantic feelings toward him, and I kept my distance. It was very weird, so I decided that the best thing was to give him space and talk to him as little as possible. With that our friendship faded, I wouldn't say we are exactly friends now. I have him as a facebook friend, and so did my boyfriend.
Later in the relationship I told my boyfriend about this friend, and what he had said about having feelings toward me. At first my boyfriend didn't seem to be affected (we were talking about similar situations he had passed), but his jealousy grew with time, and my broyfriend blocked this guy on facebook, because he didn't feel comfortable seeing his updates. However, when they see each other at Uni, they talk as classmates, and cumpriment each other.
Now we are all doing a class together, and we three, among other people, are in the same group for a project, that lasts the entire semester and requires group communication. The guy now knows that my boyfriend has blocked him, and keeps asking what happened, and if he has done something. I said that nothing was wrong, that by boyfriend just didn't want to see his updates, but he keeps asking. 
Now the situation is very uncomfortable and I don't know what to do. Please help.