Here is an article that might be of assistance.
http://www.healthlibrary.com/reading/ncure/chap64.htm
Children often get a condition called pityriasis alba. These produces mild roughness and temporary under-coloration, just as you describe. Tanning highlights the color change, which is temporary and self-limiting. You can get rid of the bumpiness with hydrocortisone 1% (over the counter in US). Once the skin is smooth, the color change will take care of itself. I don't think the mosquito bite/blister is related. That white spot from that should also go away, if it hasn't already.
Best.
Dr. Rockoff