To make sense of your question I think it's highly important to understand the context of what's going on here. At John 8:51 Jesus says, "Truly, truly I say to you, if anyone keeps My word he shall never see death."
At vs 52-53, The Jews accuse Jesus of having a demon and they go on to say, "You are not greater than our father Abraham, who died? The prophets died too; whom do You make Yourself out to be?"
Now the verse in question, vs54. "If I glorify Myself, My glory is nothing; it is My Father who glorifies Me, of whom you say, "He is our God;" vs55, and you have not come to know Him, but I know Him; and if I say I do not know Him, I shall be a liar like you, but I do know Him, and keep His word."
The Jews from verses 51-52 that Jesus claimed to be far superior to Abraham and the prophets. They died having and keeping the word of God. The Jews believed He was saying that His word was superior to God's word and that He was preeminently above the prophets and Abraham.
At vs 53, Abraham was the founder of their race, how could Jesus be greater than Abraham in their mind was unthinkable. At verse 54 Jesus is defending His statement by calling attention to the glory bestowed on Him by the Father. He denied He was glorifying himself. The Father glorified Jesus by granting the miracles He performed.
The Jews had no evidence that they were the offspring of Abraham. They did not do the works of Abraham, vs39. What the Jews said in words were not validated by their actions. Moving on to vs55, "and you have not come to know Him, but I know Him; and if I say that I do not know Him, I shall be a liar like you, but I do know Him and keep His word."
Now comes the culmination of Jesus' point starting with vs56, "Your father Abraham rejoiced to see My day, and he say it and was glad," Vs57, "The Jews therefore said to Him, You are not yet fifty years old, and have You seen Abraham?" Vs58, "Jesus said to them, Truly, truly, I say to you, before Abraham sprang into existence I am." Vs59, "Therefore they picked up stones to throw at Him; but Jesus his Himself, and went out of the temple."
When Jesus said, "Verily, verily, I say unto you, "Was born" (NASB; genesthai) is an aorist verb marking a historical point in time. Jesus was saying that before Abraham's existence He himself was existing. However, "I am" mean much more than that because He was less than 50 years old. He as a person exists in the ever present now no matter at what point on the time lie one may identify. John 1:1 and 1:30."This is He on behalf of whom I said, "After me comes a Man who has a higher rank than I, for (or because) He existed before me." That's who my God is!