Can you still workout hard if creatine kinase is high?

Resolve cause first. High creatine kinase is due to muscle damage. It would be important to determine the cause of muscle damage before working out so that you do not add to the damage.
Absolutely. The reference range for creatine kinase is set based on the assumption that you do not exercise. In my series of medical students, all the men and the majority of the women who lead even moderately fitness-focused lifestyles have high creatine kinase -- often very high. If you're healthy, be proud of yourself and keep doing what you're doing.