I think that almost everyone who dances in hard shoes has given him or herself a good kick at one time or another. Usually bruises are located on the top of the foot, having been placed there by a carelessly aimed heel during a click. Unlike muscle strains and blisters, there is almost nothing to be done to prevent them. Sure, you'll get more bruises at first, but eventually your aim will improve. O nce the bruise has occured, take some ibuprofen to reduce inflammation.
Bruises are a fact of life for Irish step dancers and are usually taken in stride.
If it doesn't improve in a few days, get it checked by a doctor. L et me once again stress the importance of taking care of yourself right before a feis. Dancing with an injury could turn a pulled muscle into a full-fledged sprain or a small blister into an infection.