Certainly can be difficult returning to running after a herniated disc. Generally, you need to wait until the disc has healed sufficiently to withstand the compressive forces associated with running. In the mean time, swimming (or walking) can often be good forms of exercise which place less stress on the disc (although this should be discussed with your physiotherapist).
A gradual return to running program is essential at the appropriate stage of your recovery and should be guided by your treating physiotherapist.
Thought you might be interested in checking out the following links on return to running and herniated discs (bulging discs):