I'm sorry to be the bearer of bad news for you but it sounds like the lens is broken. It is very possible that it was tightened too much because that would cause it to crack internally which would lead to it spinning freely. Your options are somewhat limited but I would suggest taking apart the camera in order to remove the lens from the inside. Your warranty on both the lens and camera are most likely voided already so you don't have anything to lose by disassembling it.