eye blinking

My 6 1/2 year old son has started doing an eye blinking thing . In the past he has also cracked his neck repeatedly by flexing it backwards. He stopped doing that but has know picked up the blinking thing. Is this something I should be concered about or just a "tic".

[LRM1021]

I think you would be surprised how many children get "tic" like behavior that come and go throughout childhood. It can be a response to some type of stress-- and again, it can come and go.
As long as the child is not bothered by this, and his eyes don't hurt him and he can see well, if this is his only "tic"-- I would not worry about it.