Insomnia Support Group
Insomnia is a symptom, rather than a disease, and is characterized by inadequate quantity or quality of sleep. People with insomnia complain of difficulty falling or staying asleep, which results in significant impairment of daytime functioning. Insomnia is categorized as transient (shorter than one week), short-term (one to three weeks) or chronic (longer than three...

You can counter this in a number of ways. You can learn ways to manage stress, and try to understand the kinds of thoughts that cause anxiety. That makes it easier to let them go.
Also very important is a good sleep supportive lifestyle. That means things like no caffeine after about mid-day. Watch chocolate and colas, they're loaded with it. Getting up at the same time most every day. Trying to get some good outdoor exercise most days.
If this continues to bother you after a few weeks, then it might be a good idea to see your doc to either treat or rule out an underlying medical condition. But you probably don't have one, as most insomnia is primary.