its frozen

My 5 year old for about 2 weeks now have been saying his private is frozen... But I have no idea what to tell him... We can be watching TV and out the blue he yells it's frozen again.. please help me explain what's going on

... Thanks y'all I will ask him the next time to explain the feeling.. I've told him it'll go away on its on that's about it ... And I'll make him an appointment I didn't even think he could have an infection