Playing around with an PSU is dangerous so fixing it yourself would not be a good idea. The best thing you could do do is see if the fan is touching any of the internal parts of the PSU like a capacitor(The tall cylindrical looking thing) without opening up the PSU. If the fan is not touching anything its not that big of a deal. The thing will just run warmer then before. If it's touching any internal components you should just RMA it if the warranty hasn't expired or buy a new one. In any case i recommend you replace it.