Girls, I accidentally caused serious injury to my brother. What can I do to make things at home alright again?

cassiewang
He has been learning to box recently and always challenges me to box with him, but I was in a bad mood a week ago and did not want to become his punching bag again so I did something my friend in school had told me to do which was to kick his nuts.
I do not know what happened next, but he laid down and cried even though it was just a light kick. I thought he was just pretending, but when our mother saw him she took him to the doctor because he wouldn't stop crying. I think he was injured quite seriously, because he spent a week at the hospital, and when he came back he could not walk for a couple of days.
Now, my whole family refuses to speak to me, and I am not allowed to go near him because they are afraid I will hurt him again.
I am very confused, what happened to him after I kicked him "there"? Why did he have to go to the hospital and why can't he walk? Is it possible that he cannot make babies because of it? (My friend who told me to do it said it was likely)
What should I do to make things at home better again?

Updates
+1 y
And before I kicked him, I even warned him not to make me angry but he still did which was why I kicked him there!!
Girls, I accidentally caused serious injury to my brother. What can I do to make things at home alright again?
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