Praise be to Allaah.
Usually when a person gives such a small amount of money he gives it as a gift, not as a loan, which is why he did not come to take it back. Perhaps he told you that he would come to take it back so that you would not feel embarrassed, and so that you would take this money from him and not refuse. You should respond to his kindness in like manner, and reciprocate either by giving him a gift or making du’aa’ for him, etc. You could also – so as to overcome the feelings of shyness – go to him and greet him with salaam and ask him how he is, and tell him that you have not forgotten what he did for you in the past, and thank him for it; you can tell him that you still owe him this money and that the only thing that kept you from returning it was embarrassment. If he lets you off, then praise be to Allaah, otherwise you can repay him. This is a kind of calling people to Allaah, which lets you address the importance of people’s rights and paying them off no matter how much they are.
And Allaah knows best.
May Allaah make you more keen to do good and more honest, and help you to do all that is good.