Cuts were made in the body, and irritants rubbed in, so that when the cuts healed, scars would be noticeable. Tattooing is classified with scarification. It is harmful to the body. In fact, it has in the past been outlawed because it became the means of spreading hepatitis and other diseases. Although, these verses apply first to the church, the body of believers as the temple of God, later in chapter six the individual believer is also called the temple of God, and the same principles apply to God's temple whether His workmanship of the church or of the human body.
Tattoos are wrong by reason of the principle of adornment.
Now the whole purpose of the tattoo is that it be noticeable. It is bodily adornment. Scripture principle makes clear that the adornment of the body should be governed by modesty. One should not notice a Christian because of a tattoo, but because of the spirit and demeanor of the Christian. While they behold your chaste conversation coupled with fear.