Fact. That is most likely a spirit guide or guardian. Rejoice that you have made contact with him (even if it is a little bit)! The fact that you have recognized him in your dreams is a good thing! The next step would be to get more comfortable with him and try to speak with him. (Thyna has some great tips
here.) Start by asking him his name.
It seems that since he has been in your dreams AND your instructor saw him, he might have something to tell you, or he is protecting you from something (like the spirit in your other post perhaps?).
The fact that your instructor actually said something is amazing. You might speak with her one-on-one sometime when you have free class time and dicuss these similar issues with her. Since she saw this vision, she may be more inclined toward the metaphysics and possibly studying as well. She may be able to give you some pointers as well.