My son is always blinking his eyes?

Nervous tics?: I assume that you have considered vision problems or allergies. If these have been excluded, he is probably just showing nervous tics. These are common and of no clinical significance in most cases. In rare cases they can become very complex and disruptive. This may then meet criteria for tourette syndrome. However, even then it may not be necessary to treat if he learns good management.

Eye blinking: Eye blinking is a nonspecific finding. Your son could be doing it out of habit or due to a behavioral issues. It could be secondary to eye irritation due to a myriad of causes. Check to see if he continues the eye blinking behavior when he thinks no one is watching...