Leaf disortion is a common problem on poinsettias. The following is more information.
This disorder most often occurs in the early stages of the crop. Plants develop distorted or cupped leaves. Most poinsettias will outgrow this condition, but shoots with extreme distortion may not improve. It is unclear what causes this disorder. Some distorted leaves are very symptomatic of molybdenum deficiency in other crops, and some research studies have shown that a lack of this element early in the life of the plant can result in such leaf malformations. There have been reports that deformities occurred on some plants even when molybdenum had never been deficient, so other factors could also be responsible. Mechanical injury to very young leaves can cause leaf distortion. Wind, water stress, and insects (thrips) are also a few ways such injury could occur. Rapid changes in humidity, as what occurs early in the morning when the vent fans come on, can lead to an accumulation of salts along the leaf margins and veins - resulting in leaf injury. Leaf distortion becomes apparent as these injured leaves grow and expand.
Information from the Poinsettia Problem Diagnostic Key on Physiological Disorders from North Carolina State University http://www.ces.ncsu.edu/depts/hort/poinsettia/corrective/a11.html