It sounds like it's a normal diaper rash. A bad diaper rash, but still normal. Rashes are basically an inflammation of the skin and sometimes that will lead to bumps. As the main irritation goes away the bumps become more prominent because the rest of the redness is fading. Don't worry, it should go away soon.I like to use natural baby products so for diaper cream I always used Method. You can find it at Toys/Babies R Us and sometimes at Target. It's made with all natural ingredients and it doesn't have anything that will irritate the skin further, like perfumes. I also use Earth's Best diapers (Toys/Babies R Us) because they are natural and are the most absorbent I've found. They do a great job of keeping the moisture away from baby's skin. Just keep doing what you're doing and maybe consider trying a natural diaper cream. The rash should go away soon, but if it doesn't you should take him to the doctor. Sometimes bad rashes are a sign of a yeast infection. You can also try OTC antifungal cream, I had to use that once when Audrey had a really bad diaper rash. Don't use powders like baby powder or even corn starch. They are more drying and can help clear up a rash, but the powder particles are very fine and can easily be breathed in by your baby and it's very bad when those particles get into your baby's lungs.