Got "whipped" by Man-o-war across the chest (especially the nipple) and abdomen and member. Very painful nematocyst poison. If it happens take a liberal amount of meat tenderizer (papain) and apply to the stings. The papain will denature the protein that is causing such discomfort. Try to do this as early as possible.
My Sister got stung by a Man-O-War and had to go to hospital. She said the pain was just dreadful. Sorry you had to have such a painful experience.