Story about Uways Al-Qarni breaking his teeth false
28-2-2017 | IslamWeb
Question:
Assalaamu alaykum wa rahmatullaahi wa barakaatuhu. Somebody told me that Uways Al-Qarani, when he heard that the Prophet, sallallaahu ‘alayhi wa sallam, had suffered a broken tooth in Uhud, broke all his teeth. Is that information authentic? And if so, then does that make the Shiites mourning for Imam Hussain, may Allaah be pleased with him, correct?
Answer:
All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
What that person told you is false and absolutely unfounded. Uways Al-Qarni was not a Companion to begin with, as he never met the Prophet 
. Rather, he was one of the most devout people of the Taabi‘oon (the generation that followed the Companions and met them).
‘Umar ibn Al-Khattaab 
reported that the Prophet, sallallaahu ‘alayhi wa sallam, said, "The best of the next generation (At-Taabi‘oon) is a man called Uways. He has a mother, and he had white spots on his skin (vitiligo). Ask him to pray for forgiveness for you." [Muslim] Uways came to Madeenah with the delegations from Yemen, as foretold by the Prophet, sallallaahu ‘alayhi wa sallam, so this prophecy was fulfilled. He came to Madeenah during the reign of ‘Umar ibn Al-Khattaab .
So the story that you heard is part of the illusions and myths promoted by those who go to extremes in religious matters. There is no doubt that such immoderation and going to extremes in religious matters are the source of many evils. Allah, The Exalted, forbade it in all matters. Allah, The Exalted, says (what means): {Say: O People of the Scripture, do not exceed limits in your religion beyond the truth and do not follow the inclinations of a people who had gone astray before and misled many and have strayed from the soundness of the way.} [Quran 5:77]
Moreover, Ibn ‘Abbaas narrated that the Prophet, sallallaahu ‘alayhi wa sallam, said, "Beware of going to extremes in religion; those who came before you were destroyed because of going to extremes in religion." [Ahmad and An-Nasaa'i]
It is inconceivable that Uways 
would have disfigured himself and inflicted such harm on himself; in fact, such an act would only be done by an insane person who has lost his mind.
For form information, please, refer to fatwa 82011.
Allah knows best.