It's called a Fasciation and there are a number of factors that can cause this. Usually for small hobby growers it's not a huge concern. If your interested in learning more about your odd looking bud look into Cannabis Fasciation's it is not Polyploid as this is a different thing.
Fasciation (pronounced /ˌfæʃiˈeɪʃən/, from the Latin root meaning "band" or "stripe"), also known as cresting, is a relatively rare condition of abnormal growth in vascular plants in which the apical meristem (growing tip), which normally is concentrated around a single point and produces approximately cylindrical tissue, instead becomes elongated perpendicularly to the direction of growth, thus producing flattened, ribbon-like, crested (or "cristate"), or elaborately contorted, tissue.
Polyploidy is the state of a cell or organism having more than two paired (homologous) sets of chromosomes. Most species whose cells have nuclei (eukaryotes) are diploid, meaning they have two sets of chromosomes—one set inherited from each parent. However, some organisms are polyploid, and polyploidy is especially common in plants.