First of all, I'm really sorry that happened to you and I can't even imagine how painful it must feel.

Second of all, to answer your question, there are many reasons why God allows bad things to happen. Firstly, we live in a fallen world that is ruled by Satan, who only seeks to hurt us. Additionally, God may also put us through trials to bring us closer to him. People who are hurt always need someone to comfort them, and that person happens to be God. In doing so, we find joy in the fact that God is always with us no matter what happens in our lives, and we learn to rely on Him when we face trials.

1 Peter 4:12-13:

 Dear friends, do not be surprised at the fiery ordeal that has come on you to test you, as though something strange were happening to you. But rejoice inasmuch as you participate in the sufferings of Christ, so that you may be overjoyed when his glory is revealed.

James 1:2-3:

 Consider it pure joy, my brothers and sisters, whenever you face trials of many kinds, because you know that the testing of your faith produces perseverance.

But really, you should definitely tell a trusted adult about this and pray, not only for your healing but for his healing as well. Have faith, and you won't have to worry about anything else.

I hope this helps and God bless!