I Have Poison Ivy On My Lower Arm Which Yesterday

I have poison ivy on my lower arm which yesterday not only became blistered but also swolen. A nurse friend told me to go to urgent visit, but it is now Saturday afternoon and the one near me closed at 1 PM. Is this something that needs to be seen and treated right away, or can I wait to go to my doctor's office on Monday? I am putting calomine lotion on it, but don't know anything else to do to treat it.