The New Testament and the Nicene Creed are deeply entangled with each other. The wording and the concepts in the Nicene Creed come from the New Testament—in fact, one of the most important debates at the Council of Nicæa concerned whether it is proper to include a word in the Nicene Creed that does not occur in the New Testament. On the other hand, at the time that the Church issued the official canon of the New Testament, it customarily compared writings to the Nicene Creed to determine if they were orthodox. So you are correct if you say that the Nicene Creed proceeds from the New Testament, and you are correct if you say that the New Testament is certified by the Nicene Creed.
By affirming certain books as Holy Scripture, it does not follow that the Church rejected or even banned all other writings. The Church continued to use the other writings, if they were orthodox, but not with scriptural authority.
Here is a brief, comparative history of both the New Testament canon and the Nicene Creed.
The History of the Canon
The History of the Creed
85
130
140
Marcion’s New Testament includes the Epistle to the Hebrews and the Pauline epistles, except the epistles to Timothy and Titus. He includes Luke, after editing it to remove everything Jewish. He rejects Matthew, Mark, and John.
150-160
200
In some areas, a few people object to the following books, mainly because of uncertain authorship. The main reason Revelation is included in this list is because of its heavy use by heretics:
Hebrews
2 Peter
Jude
2 John
3 John
Revelation
A few people felt that the following books should be part of the New Testament:
Epistle of Barnabas
The Epistles of Clement
The Shepherd of Hermas
323
325
367
381
382
431
589
796
807
1054
The Great Schism
Rome excommunicates the Eastern Church.
The Patriarch of Constantinople retaliates by excommunicating Rome.
1100
1274
1439
first among equalswith the other patriarchs. The Roman Catholics refuse the papacy deal, a lone Eastern Orthodox bishop stands on principle about the filioque clause, and the reunion fails. (The Eastern Orthodox reason that if this Council had succeeded, it would have been a true Ecumenical Council, and that would have given it the authority to amend the Nicene Creed.)
1500
1965
The Great Schism Ends—More or Less
On 7 December, Pope Paul VI and Patriarch Athenagoras meet. They issue a joint statement in which they deplore the events that led to the schism of AD 1054 and revoke their mutual excommunication. However, they do not establish intercommunion or resolve the filioque controversy.
You can read more details about the Nicene Creed.
Ancient Stuff That Is Not in the Canon
The so-called infancy gospels try to add biographical information about Jesus’ childhood and sound more like the Adventures of Superboy than anything credible. They are not even written in the literary form of a gospel; that is, they are not evangelical tracts. They are not in the canon because they were written centuries after the canon was accepted by consensus in its current form.
The Gospel of Thomas is a misnomer, because it is also not in the literary form of a gospel. It is actually a collection of Gnostic sayings (logia) attributed to Jesus. That in itself is not enough to exclude it, but the early church did not use it and the New Testament writers explicitly opposed Gnostic incursions into the church. The ancient church historian Eusibius mentions it as a non-canonical book. It was lost due to neglect and perhaps a lack of interest until it was recently discovered. It is compatible with what we used to call new-age thinking,
which probably accounts for its popularity today.
The Acts of Paul and Thecla are not included in the canon, because it depicts Thecla as Paul’s constant companion as they go from place to place. Thecla is unknown to the New Testament. If she had been Paul’s companion, she (like Phoebe, Priska, and Lydia) would have been mentioned in the canonical Acts. No one today complains it is not part of the canon, probably because it advocates an severe form of ascetisicm that is not only uncharacteristic of Paul, but is impractical and unpopular today.