[souffle]

They are very mobile and can be withdrawn in into the abdomen. Are those even going back up ILMH? Is the room very warm at all or is he just out a warm nest and relaxed?
I would try taking him in to a cooler place first to see if he can retract them and if not and they feel hot and swollen he is going to need a vet. Orchititis is an infection of the testicles and it is very painful but they really do swell with this and they cannot retract them. It responds well to antibiotics normally.
In the pics it doesn't look like that just now I don't think but photos are not a good way of diagnosing anything and I haven't examined him nor am I a vet so you need to watch him carefully. They also tend to act out of character and are ill and lethargic with orchiditis.