Get first_name and last_name on user_register hook

I have multisite running with 4 sites. One of them has woocommerce. Customers have option to create account while checkout. I have custom analytics where registered customers are labeled with wordpress user ID (get_current_user_id()). Customers without account have default ID of 0. My analytics allow me to add first name, last name, email etc… to customer according to his ID. I would like to add this information right after they make account. I used user_register hook to do this job but it is not working.