I will offer a few things that work for me when fighting it:

-level the area around the skull a bit to get rid of as much standing water as you can (I usually do a circle around the skull so I can kite it around if need a breather while still getting some cover)

-clear out any enemies that might be in the area before you start the fight (don't need uninvited adds)

-pick up on its attack rhythm and don't get too greedy on trying for more hits; mine is something like; block,hit, hit, hit, block, hit, hit, hit, SPEW, kill adds, back up, repeat

-when it spews kill the adds then back out of the poison cloud (no reason to stand in it)

You will do fine, just take your time.

And @jonnin chuckled because later on you will come back for more iron (you use it in the Plains), but it will be so easy to get its a non issue; I would not hold up progressing just to stockpile iron, but that is me.