Squeaking trucks are by no means a serious issue and is a common problem, it just means your bushings are a little dry. The simple solution to this is to apply a small amount of lubricant to the bushings. Do not over apply lubricant to these parts, once the bushings are sufficiently lubricated and you no longer hear a squeak, dry off any excess lubricant. Excess lubricant lying around these components is no harm however it can cause dirt and grit to become stuck and subsequently damage the component.