Cats will sometimes feel warmer than we do because their normal body temperature is warmer. Their normal is 100.5 to 102.5 degrees. The best way to know if they have an increase in temperature is to take their temp with a thermometer. That is not always the easiest thing to do though. But he may have been cuddled up in some blanket or in a warm location and that also will make him feel warmer for a little while.
Usually if cats have a fever they are more lethargic and eating less. So if he is eating, drinking, urinating and having bowel movements normally, not having any sneezing or trouble breathing, active as normal and seems like his usual self, then he is probably ok. But if you are concerned, you can take him in for a check up and they will take his temperature and give him a physical exam.