molluscum contagiosum is another possibility.  You can look into this as well.  They can be clusters of pimple looking bumps.  I believe my son has them as well & I will be taking him to a pediatric dermatologist at the end of this month.    They say it's a viral infection commonly called poxvirus.  Non contageous, but I heard you should let them go into a pool with it because it can spread through the water to other children & to different parts of the body.    Also, if this sounds like what your son has...  DO NOT SQUUEZE THEM/POP THEM...  it has to hurt #1 & #2, it may spread & make more bumps either in that area or to other areas on the body.    They say that once their bodies build up an immunity to it, they should go away (they say 2-9 months, but my son has had them for about 2 yrs.  Wondering if your son attending a new school or if he swam this summer with younger kids.  Could've been where he contracted it, since he is 8 yrs old.    Look into it, and I hope you find a solution.  When you are stumped, you can call a dermatologist.  I am sure they will know best & give you some suggestions.