Hi

I think I've experienced this just once.
You may have to have someone hold the bolt real solid or maybe put a cloth around it and use a vice. Anyway, what you need to do is to push back the cocked indicator. It is under spring pressure as it moves with the firing pin so there is a internal spring you are pushing against.
It doesn't take long to do, just push the cocked indicator back and then the front portion of the bolt will be able to rotate.
Hope this helps.