I think I would cover it with a circle made from the same red fabric that you have used in the block. Oh and look .... there are circles on the red fabric. Perfect! By the way, it is a great block with wonderful use of colors/fabric! When I try to match up points like this, I usually have to baste the piece first and then fiddle with it until I can get it right .... or at least close. That was a tough block to do.