What to do about Dad obsessing over things?

My dad is 86 with 2 forms of cancer. He just came back home after a month in Hospital/Rehab. He went in due to being septic due to a UTI. Anyway he did ok in Rehab but has leveled off on getting any stronger. He is now bedridden. The day he came home he started to have bowl problems I know he was in pain but he was also putting his hand and fingers where they don't belong. It has been a mess. So today the bowl issue is over and almost within seconds he is now obsessing over a small bump on his head. I have nurses that have checked him they say it's most likely a pimple or in grown hair. It's just every time I go check on him he complains about this bump now. Just once ok maybe twice I'd like to go in say hello and visit for a few mins without his complaining. I know once this passes there will be something new for him to complain about. He had only been back a few days and I'm exsauted. The bowl issue really did me in. How do any of you deal with constsint complaints??