We had a batch of robins hatch and leave. We left the nest not knowing if it was okay to knock down. I know now it is. But we have an issue.

I was hanging up laundry and had to chase a robin off a swingset in order to get to the laundry line. Later that day it flew so close it hit its wing on my ear.

After about a week, we all went outside saw the robin on the tree where the nest was staring and screeching at us. It came closer and closer and we got the message and went inside. But the next day, it attacked 2 others.

Is this because we left the nest up? Will we get attacked if we look in the nest to check if its safe to knock down?

Sounds like the Robin has eggs/young in the area. How long ago did the young leave the nest? If it wasn't that long ago, the adult could still be protecting them if they are in your yard. If it has been more than 3-4 days since the young left the nest then you might be dealing with round two. Robins often raise two broods a year. And if they were successful the first time around, they are likely to come back. They aren't likely to use that same nest, but they might build a new one nearby. Check the first nest if you can reach it. A mirror taped to a painting pole or broom works pretty well. If there's nothing in the nest you can pull it down. But be on the lookout for another nest... and for the Robin...sounds like he or she will be on the lookout for you. : )