Q: Is it permissible to pierce your tongue?
A. Piercing the tongue is sinful, because it is not an Islamic practice, rather a custom borrowed from the non-Muslims, but it does not fall under the category of major sins. Doing this is, therefore, akin to committing a Makrooh Tahreemi act. For this one should make Taubah. The position of these types of sins (i.e. Makrooh Tahreemi, which is close to Haraam) is that if one’s good deeds are more, then these sins are automatically wiped out. If not, then these lesser sins will all weigh against one on the Day of Judgment. Punishment depends on what Allah Ta’aala decides. If something is sinful, big or small, the duty of every good Muslim is to abstain there from.
Mufti Siraj Desai