Try a healing brush before the clone, should work out fine in photoshop if you retain the full res picture... zoom in large and use large soft brushes to paint out things carefully. the cloud doesnt look too clustered, so its do-able...
good luck
btw, Is that a lens flare from no hood or is it the filter? I had same problem before on the harbour night shots, now I rarely use a filter for long exposures at night. A filter (no matter if multicoated) gives a cance to flare under this tricky night lights.