So this is what I did to rectify the problem. First, do a Network Reset, this resets all network settings to factory, wait for the iPhone to reboot. Then, do a Reset All Settings, you won't lose data or media, but if you have a passcode on, it will be erased, but is easily fixed when it reboots, also note your iPhone's background will be reset to the "Water on Window" background, so you will need to change that as well, but that's about it. Wait for the iPhone to reboot, then go to Settings>General>Network>Personal Hotspot, and turn it on, then immediately connect a computer to it, then afterward disconnect, and it should still show up in the settings on the iPhone, and visible to any computer with WiFi capabilities. I just had this happen to me a few minutes ago, and this fixed it. Try it.