that was a cone... won't hurt it much... should keep right on growing unless other damage was done (like to the trunk)

Most Cycas species put out pups or side shoots when the top is damaged.

Thanks for the information. I potted six pups from the base of the large palm during the transplant but I was most concerned about large plant.

What you should worry about is the stress of leaving the leaves on, if you did that, and the possible wounds you made on the stem when you removed the offsets, which WILL kill the plant if not properly treated. Just in case you think you might not have done something right, here is a page I found on a website that talks about both these subjects.
http://cycadjungle.8m.com/cycadjungle/Most%20Frequently%20Asked%20Questions.html