I'm 33. I masturbated on the 11th day after 700 grafts hair transplant. Is that OK?

Yes it is ok to do pretty much anything at this point. If it was just a few days post op I would worry about popping of grafts.

Hello, please see below.We advise to avoid sexual activity for first week after hair transplantation.  The rationale is to avoid increasing blood pressure.  There are no studies supporting this however.  
Best 
Anil Shah MD

Since it was on the 11th day, and you are over 30 years old, and it was only 700 grafts it should be fine.  

That isn't going to be a problem.  At 11 days, you mainly just want to be sure you are protecting the grafted site.  Hope that relieves you of any worries.

There are very few limitations after a hair transplant procedure and sexual activity is not one of them.  Restrictions after hair transplant mostly have to do with the type of the procedure and it is important to review them with your doctor.