Nice block! I think you are on a fast learning curve and just need to make a few more blocks. I have made these blocks and they are fun but challenging. It looks like you have nested your seams well according to the tutorial. Your seams look great! The corner is fine. I would not have seen it at all if you had not mentioned it. Did you square and trim your HSTs? This is one of the things I continue to "live and learn" ...
Pat