The Bible says that our body is the temple of God. God treats this very seriously and so should we.
1 Corinthians 3:17
If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are.
1 Corinthians 6:19
What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?
In the Mosaic Law God forbad the Israelites from putting marks on their body
Ye shall not make any cuttings in your flesh for the dead, nor print any marks upon you: I am the LORD.
Although dispensationally speaking the above verse applies to the Old Testament Jews. However, there is always something that can be learned passages that don't apply to us today.
2 Timothy 3:16
All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness:
Another thing we must take into account is the way we spend our money. Tattoos cost hundreds, if not thousands of dollars and God wouldn't approve of us spending that money on something that won't even profit or benefit us. It would be a much wiser choice to spend that money on the poor and God would reward you greatly at the Judgement Seat of Christ for such a thing.
21 He that despiseth his neighbour sinneth: but he that hath mercy on the poor, happy is he.
31 He that oppresseth the poor reproacheth his Maker: but he that honoureth him hath mercy on the poor.
He that hath pity upon the poor lendeth unto the LORD; and that which he hath given will he pay him again.
He that giveth unto the poor shall not lack: but he that hideth his eyes shall have many a curse.
The righteous considereth the cause of the poor: but the wicked regardeth not to know it.
After reading all these verses there should be no doubt that getting a Tattoo is a sin. It's not the worst sin. The Bible never gives a death penalty for marking your body. But, the money used to get a Tattoo could be used for much greater things. The Bible also tells us to not be conformed to the world
And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
Tattoos are very popular among nonbelievers and if a Christian were to get a Tattoo that wouldn't make a good example of God. Regarding having Tattoos removed. The same thing applies for how wisely we use our money. Having a Tattoo removed is also very expensive and a very difficult process. It would be much wiser to use that money to support the poor.
May there be a love for God's word in your heart, amen.