No, you do not have license to be rude just because you are in pain.
Sometime it cannot be avoided and in those cases, once someone regains their self control they are ashamed at their behavior and offer apology for it. You seem to want to use it as a justification for having a fight with your roommate.
Yes, he was rude for yelling to you from another room particularly when he did not know what was going on. FWIW, running a smashed finger under cold water can help too.
But, you turned all our anger of the situation on him and made it worse. Understandable, but not OK. The two of you should probably sit down and talk about it so that you an both apologize to each other and so that you can explain that you don't like being yelled to from another room whether you are being stubborn about something or not. That seems to be the crux of the problem.
I like this post.
I agree that being in pain is not a given pass to being rude, after all is said and done an apology for your (generic person in pain) angry words/rudeness is in order.
I also agree that when you're in pain, words tend to spout out . . . words that you would never use in normal situations. (I'm thinking of all the funny stories of a woman in labor lashing out at her husband, saying cruel things to him "This is all your fault!" etc.)
justify your angry words with an apology "I'm sorry I said those things to you, but I was in pain. I wasn't myself and just lashed out."
think that your angry words are justifiable by expecting
the other person to immediately know where you were coming from. "He was a donkey and should know that I said what I said because I was in pain."
The person to whom you lashed out at should accept the apology with no ill will towards you.
Angry words while in pain are understandable.
Curious -- you said that you didn't talk to each other for two days? How did you get back to talking? Did one or the other apologize or was it back to normal without mentioning the incident?