Pear Tree Problems

I have a 3 year old miniature pear tree in a pot and have noticed that some of the leaves on the ends of the branches have curled in on themselves. I've pulled a few off and unfurled them thinking it was aphids or a caterpillar but couldn't see anything. The rest of the tree looks healthy with plenty of fruit forming. Don't know if it's anything I need to worry about.

Any ideas anyone?