The biggest hazard would have to be any macroscopic particles left over. 

Gamma rays, X-rays, and other ionizing radiation would spread out at the speed of light, or nearly so for electrons, alphas, etc., and within moments be less than the radiation that always present in space. After an hour, any such radiation will be smeared out to a volume as large as the orbit of Jupiter. I.e., it's effectively gone. You'd have to worry more about minor solar flares than space nukes.

On the other hand, although most of what's in the immediate vicinity of the explosion would be vaporised to atoms (or parts thereof), it seems possible that you could end up with significant amounts of debris. Perhaps the solar wind would blow the smaller ones away, much like the effect with a comet, but some of the larger chunks would present major navigational hazards. NASA gets very concerned when millimeter sized bits float away in orbit. Obviously anything larger will be more of a concern. If you're moving around at planetary speeds, 10's of km/sec, the kinetic energy in such space junk could easily put a hole your hull.

Effects of nuclear explosions in space?
In a project of mine I took a 24-bit bitmap image and I performed LSBit steganography over it (saved a black and white image inside each of the planes R, G, B) using pixel shuffling and xor encryption.

Is my stenography easy to detect? And what would it take to conceal it? 
