In general, it is safe to dive while taking an antibiotic or corticosteroid medication. If a wound infection is more than minor or is expanding, however, diving should be curtailed until it becomes minor, is no longer progressing and can be easily covered with a dressing.
In or out of the water, corticosteroid medication should always be taken with the understanding that a rare side effect is to cause serious deterioration of the head ("ball" of the ball-and-socket joint) of the femur, the long bone of the thigh.
For more information on marine life injuries, see the complete article by Paul S. Auerbach, M.D., M.S. on Marine Life Trauma from the Jan/Feb 1998 issue of Alert Diver.