when ever i launch minecraft the screen goes black. My cousin put a texture pack on and after he did that my minecraft wont work anymore

Put the summary of the bug you're having here

What I expected to happen was...: my Minecraft would open
Describe what you thought should happen here
Let me onto minecraft
*What actually happened was...:*wouldnt load
Describe what happened here
the screen goes black everytime i launch minecraft
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...