sold my water damaged iphone4 still logged into icloud

so i sold my iphone4 on ebay. it was water damaged and it was set as a new phone but the thing is that i forgot to log out of my icloud. which means that he could back up my personal info back into that device, right? he hasnt received the phone yet. i checked on usps tracking and i change my password this morning for icloud. will he need to enter my new icloud password again for him to access the back up? cause i am worried.