Did Jesus encourage self-mutilation? is it a sin to refuse it?

No, he was using hyperbole to make a point.

He was making a point about the awfulness of a fiery Hell.

How many Christians have you seen walking around with missing eyes, hands, or arms?

Jesus was giving counsel on morality. Staying morally clean requires effort. The eye spoken of by Jesus represents the ability to focus our attention on something, and the hands relates to what we can do with our hands. If we are not careful these body parts can cause us to stumble and hurt our relationship with God. When we are tempted to disobey God, then we need to take strong action to restrain our eyes from concentrating on immoral things. Also, our hands can cause us to violate God’s moral standards.

Jesus was saying we need to make changes comparable to tearing out the eye and throwing it away to fight against immoral fleshly desires. If not it could cause us to loose out on life.

Good question.

Many christians are of the view that Jesus was only speaking symbolically when he said:

(Matt 5:29) And if thy right eye offend thee, pluck it out, and cast it from thee.

v:30 And if thy right hand offend thee, cut it off, and cast it from thee.

They reason that Jesus didn't really mean for people to self-mutilate themselves just because their eyes or hands caused them to sin.

Also according to them what if a person didn't have a right eye or hand on their body to pluck out in the first place?

What is the context of Jesus' words here?

Jesus was speaking to his fellow Jews about a real place in Jerusalem called in the Greek "gehenna"

Our English bibles use the words "hell fire" for "gehenna" (Matt 5:22) but its the same place in either language.

Gehenna was a place in Jerusalem where dead animal bodies and rubbish were burnt up by fire -- in other words a rubbish dump.

In O/T times it had a more sinister use, pagan rituals and human sacrifices were performed their where babies were thrown alive into a burning fire in a location called the valley of Hinnom or gehenna (2Kings 23:10)

Jesus knew of this place and used it as a warning to any unrepentant Jew that their bodies would been burnt up by fire after death in this hell-fire/gehenna.

This would have been a real humiliation for any Jew and their family to have a members body burnt up in a rubbish dump!

It is possible that after death that Jewish persons body parts i.e  right eye or hand  (it could be the left as well !) would be cut off their bodies  by a family member and the rest of their body thrown into this hell fire.

That is the context of (Matt 5: 29-30) and of this hell-fire/gehenna.

It has got nothing to with the unsaved going to a burning hell-fire in eternity today because it only existed in Jerusalem in the first century until it was destroyed by Nero and Rome in 70 AD.

i dont think he meant it that way

The context suggests that nothing should get in one's way to heaven.