I was praying and in the last Rakat a drop of blood was hanging from my nose but it didn't fall down. I completed my prayer, but I am not sure that if I did the right thing.

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. All the Muslim scholars agree that a little drop of blood from the nosebleed does not nullify Wudu. In your case your prayer is correct. So you do not need to repeat that prayer as long as the amount of blood was very little .In fact even those scholars who believe that bleeding from any part of the body annuls Wudu, stipulate that the amount of blood should be abundant.
Anyway, the preponderant opinion of the Muslim scholars is that bleeding from an unusual place does not abort Wudu even if the amount of blood is large. In this case the praying person should stanch the flow of blood repeatedly and not allow it to accumulate. It is narrated in Muatta that Abd ar-Rahman Ibn Harmala al-Aslami said, "I saw Sayeed Ibn al-Musayyab with his nose bleeding and blood poured out of it so that his fingers were all red from the blood coming out of his nose, and he prayed without doing (repeating) wudu." Imam Malik also reports in his Mutha from Abdur Rahman Ibn al-Mujabbar that he saw Salim Ibn Abdullah with blood running from his nose so that his fingers were all coloured red. Then he rubbed the blood and prayed without doing wudu. Allah knows best.