Unless you have recently jailbroken your phone you have nothing to worry about your device being "hacked". Simply opening a link is not enough to hack someone, now if you opened a link and started typing information into an unknown page you thought was related to Apple or another provider that turned out to be false, I would worry more about personal information and numbers provided in that form of being compromised. If you did open a window and start supplying any type of login information, change those details immediately. If you just opened it and then immediately closed it... carry on. You may need to reset your browsing history and temp files but that would be the worst of it. SETTINGS > SAFARI > CLEAR HISTORY AND WEBSITE DATA. Don't forget to close out all your tabs regularly too, press and hold on the overlapping squares at the bottom of the window and close all tabs.