dont glue it, admit it, fans are cheap, try overclockers.co.uk

there are 3 parts: the fan, the heatsink (the metal part the fan is screwed on to), the CPU (your processor chip under the heatsink)you should change the fan part. having one blade off will spoil the centrifugal balance and increase friction and wearing off of the fan's parts. Eventually it will spoil the motor and stop working.You can just buy the fan parts which are quite cheap, and are screwed onto the heatsink using 4 screws. No heat compound paste is needed.Most of the time the shops will sell fan parts together with a customized heatsink. Brands like Coolermaster and Thermaltake make good models but make sure they match your processor and motherboard as the size of the heatsink connector differs.The heatsink itself needs to be clipped on to your motherboard with its own inbuilt clip, and some heat compound paste must be applied at the contact point of the heatsink metal and your CPU (processor)

If you leave it that way, it will keep on vibrating until the bushings or bearings will wear off and break.A computer fan usually has 7 blades, but if by any chance your fan has an even number of blades, try breaking the blade opposite to the one already broken, if not, (odd number) try cutting the two opposite blades in half. Keep in mind that you want to balance the fan, just like a car tire. Good luck.