I don't think the disciples realised straight away that Jesus was God, or even that Jesus was the Messiah. However it would seem that they all had the revelation that He was truly God at some point during Jesus' ministry.
Peter writes "our God and Savior, Jesus Christ" in 2 Peter 1:1
Thomas addresses Jesus as "My Lord and my God" in John 20:28
John referred to Jesus (the Word) as God in John 1:1
Paul called Jesus "the great God and Savior" in Titus 2:13
Jesus was referred to using several titles in the New Testament.
As well as being called Lord, He was also referred to as the Christ (anointed One), Teacher, High Priest, God, Son of God, Son of Man, Lamb of God, etc. Each of these terms is translated from it own specific word, or words, in the Greek (kurios, Christos, Rabbi, theos, etc) and it is very unlikely that they were mistranslated. Each of these terms reveals something of Jesus ministry and nature.
I am a human being; a woman, but people do not actually call me that. They call me by my name or other titles, example: mum, teacher, etc. Jesus is God, but it is usual to call him by either his Name or by other titles such as Lord or Christ.