There is no direct evidence that links shoulder dislocation and decompression sickness. It is possible that residual swelling in surrounding joint tissues may inhibit the offgassing of tissue nitrogen, but this does not necessarily mean you are at an increased risk for decompression sickness. It is more likely that you would reinjure your present injury as the result of the repetitive arm movements associated with scuba diving, such as lifting and putting on equipment or perhaps entering the dive boat.
In general, normal scuba activity requires a full range of motion in both the hips and shoulders. Since you are expected to perform self-rescue in the open ocean, a minor physical impairment may be magnified in such circumstances. There is also the risk of confusing the aches and pains associated with your injury with a case of decompression sickness should you experience symptoms after your dive. When your physician feels your injury has stabilized and your rehabilitation therapy is completed, you may wish to discuss the work of diving and the risk of reinjury with your doctor.