Second, we don't know that the Apostles needed baptizing. The Great Commission was given to them, and it is where the Lord commanded baptism. Perhaps they were "grandfathered" in due to their 3 years of training.
Third, we know that the Apostles did baptize under the direction of the Lord, prior to and after the crucifixion. How is it that He would command this of those who were unworthy? After all, didn't He seek out baptism from John at the commencement of His public ministry?
Fourth, while we do know that The Lord commanded the Apostles to baptize people. We don't know that they themselves needed baptizing. After all, if this were an issue wouldn't Jesus have said something like, "Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you always, even unto the end of the world. Oh, and before you do all this, baptize yourselves first. Amen."
He didn't say that, so the implication is that, however it was accomplished - baptism or otherwise - the Apostles were added to the Church. Perhaps they were baptized earlier, possibly later, or possibly not at all.
Unless you think John the Baptist lied and could he also of lied about Jesus being the Christ? Was he a prophet of God?
Second, we don’t know that the Apostles needed baptizing.
Some were followers of John the Baptist and would have been baptized by him.
Jhn 1:35 ¶ Again the next day after John stood, and two of his disciples;
Jhn 1:36 And looking upon Jesus as he walked, he saith, Behold the Lamb of God!
Jhn 1:37 And the two disciples heard him speak, and they followed Jesus.
Jhn 1:40 One of the two which heard John [speak], and followed him, was Andrew, Simon Peter’s brother.