Creatine kinase is an enzyme found in various tissues in the body including the heart, brain and skeletal muscle. When our muscles become damaged, increased amounts of creatine kinase are released into the blood.
There are three forms of creatine kinase in the body:
Creatine kinase helps to create a rapid source of energy which can be used for muscle contraction. However, if the muscles become stressed, injured or inflamed then they leak cytosolic enzymes including creatine kinase. Common causes of elevated creatine kinase levels are muscle injury, myocardial (heart muscle) injury, infection or drug-induced myositis. 
Elevated creatine kinase can be a sign of muscle damage which can be incurred after intense exercise. Elevated levels are consistent with muscle pain or weakness. Your levels can also be elevated after a heart attack. Very high levels can lead to renal failure.
Muscle recovery can be aided by eating a nutritionally balanced diet and ensuring you get sufficient recovery periods between exercise.
Avoidance of nutritional deficiencies particularly energy, protein and micronutrients is important. Eating a diet which is based on whole foods such as whole grains, fruit, vegetables and lean meat should be encouraged as this can aid the healing process. 
Exercise can increase creatine kinase levels. Low-intensity exercise causes less damage than high-intensity exercise. 
You should ensure that you have an adequate recovery between exercise sessions. If you experience muscle damage due to exercise a break of at least one week should help to reduce creatine kinase levels. 
 Leverenz, D., Zaha, O and Chung, C, P. (2016). Causes of Creatine Kinase Levels Greater Than 1000 IU/L in Patients Referred to Rheumatology. Clinical Rheumatology: 35(6), pp 1541-1547.
 Tipton, K, D. (2015). Nutritional Support for Exercise-Induced Injuries. Sports Medicine: 45, pp 93-104.
 Baird, M, F., Graham, S, M., Baker, J, S and Bickerstaff, G, F. (2012). Creatine-Kinase and Exercise-Related Muscle Damage Implications for Muscle Performance and Recovery. Journal of Nutrition and Metabolism.
 Kindermann, W. (2016). Creatine Kinase Levels After Exercise. Dtsch Arztebl Int: 113(9), pp 344