This happened to me in school holidays at age 14 the wonders of masturbating :P didn't have a shower for at least a week and lots of masturbating=lots of sweat.. makes sure your sack stays clean it shouldn't be serious it's just some sort of fungus make sure you get rid of it before it gets bad.
Maybe you put the wrong kind of cream?
As you know that is a very sensitive area, so it's normal that some products irritate it more than others. I remember that I used to bath with what seemed like a pretty regular soap, but every time I washed my privates with it I would get really dry skin in there the next day. Eventually I changed the soap and it stopped happening.
Give it a day or two and see if it gets better. Only use some kind of simple moisturizer instead of creams, see if it helps.