My central air unit is working but the compresser will not shut off and there is frost on the pipe help.

When you say compressor,I guessing u are saying the fan motor outside also will not cut off, is this correct?
If so you probably have a stuck contactor(behind the panel of the condenser unit)
Or either a shorted low voltage wire that runs from the airhandler to the condenser
The condenser runs on high 230 volts electric so I recommend unless you are experienced that you call out the pro`s,, the power must be turned off if you attempt to remove and replace the contactor

Yes, is the fan still running? How about your air handler blower? I would definitely check the contactor.