is hole in the head contageous and if one of my fish has it and the other does not...will medicating tank hurt my healthy fish?

you wouldt be better of putting the sick fish in a quarantine tank and treat only the sick fish.That way your healthy fish surely won't suffer and you will need less medication
One of the main causes of HITH is poor waterconditions.
Can you pleasepost results for ammonia, nitrites, nitrates and pH?
Meds will do your fish no good ,if the water isn't in pristine condition.

x2 there deejay

HITH isnt catching from another fish, however the most common cause is poor water quality. Some fish will get it before others but they will all get it if the poor water conditions continue.

If you put a fish with HITH in a tank with good water quality then the others wont catch it

as everyone said you can treat hole in the head
all you can do is keep water extra clean

welcome on board deejay!

can you post a picture so that we can have a good glimpse of his/her condition.
early stage of HITH can be cured by just keeping your water in good shape
coupled with varied foods.