Seam binding Peter Pan collar for Mum

This is another post of a top I sewed for my mum recently. My mum went to Chinatown last weekend to get this polka dot cotton fabric which is made in Japan. For this top I decided to add blue binding around the collar so as to make the collar more outstanding. This is my first time sewing mitered corner, I followed tutorials on YouTube on how to sew mitred corner and it turn out presentable on the right side of the collar (the wrong side is horrible as I have difficulty sewing the bias tape to the fabric). For the bias tape I used cotton bias tape instead of satin bias tape.

The fabric wrinkle after wearing it for a day at work.