My minecraft wont start

When ever i try to start my mine craft it says this error Unable to save download. 1.12.json
Name: 1.12.json
URL: https://launchermeta.mojang.com/mc/assets/1.12/98c430c16a705f18a58a281b27caabf3ef09d40d/1.12.json
Error details: Attempting to move successful download to C:/Users\Jacob's PC\AppData\Roaming\.minecraft\assets\indexes/1.12.json
The process cannot access the file because it is being used by another process
Filename on disk: 9321-9cec-fa2d-0285
Path: C:\Users\JACOB'~1\AppData\Local\Temp\9321-9cec-fa2d-0285
Exists: file
pls help me i want to play bad this has been happimg for like 2 months and i can not play