I have a blackbird nest in a very vulnerable place. Looking for advice please

I had cut up a lot of old branches I’d been meaning to get rid of for an while and put it into a builders bag to take to the local skip. It was there for a week. A day before I was due to take it to the skip I noticed a blackbird entering and checked inside, she had built a beautiful nest. This morning she laid an egg. I’m very worried as it’s in a very vulnerable spot, just on the top layer of branches in the builders bag. We have magpies that hang around the garden and are loitering around the bird box with great tits in, with babies approx a week old. Is there anything I can do to prevent anything happening to this nest? I will upload photos. Thank you