They used to occur in chronic ear infections etc but almost never anymore so I'd be surprised if anyone less than 70 could tell you how it feels. The mastoid bone is kind of porous like very hard sponge if I remember my anatomy. So if there is an infection if it is producing gas or otherwise expanding I think it can be quite painful. If he is upset likely secondary to pain. In which case pain meds would be the best thing. If he really isn't coping well an ENT surgeon would be the most helpful person. Many years ago they used to open up the cavity and let it drain into the ear I think but antibiotics were not as good hopefully antibiotics take care of it. Sorry about your dad.
He lost his balance and has all over weakness and his blood pressure is all over the place from alarming high to low. He is dizzy and more confused than normal. Based on that they did the CT to look for stroke or brain bleed and found his mastoid full of fluid. He was in the ER for a different reason earlier in the week (peeing blood). So his health over all is pretty poor - but he still tells a joke and laughs at them so he is in good spirits. He says he's not in any pain. But I had to get him a wheelchair today. I was just hoping for some first hand experience with this as I had never heard of it. It sounds like there is a small probability rather than an infection a mass of some type could be causing it too.