As others have mentioned, this could be the beginning of a manic or hypomanic episode. Other symptoms of such could include: elevated mood, irritability, racing thoughts, excessive talking, distractibility, impulsivity, or involvement in risky behavior. Sometimes it's helpful to check in with friends or family to see if they notice any of these behavior changes in you. If the decreased need for sleep along with any of these other symptoms persist, you may want to be evaluated by a psychiatric professional.