What Causes Itchy Red Bumps On The Skin?

My nephew had what looked like a sweat pimple on his stomach, my sister tried to sqeeze it and now it is infected. We took him to the doctor who couldn't diagnose, but put him on Cephalexin. Just last night now I found the same looking red bumps on my stomach and my lower back, I found 2 more this morning on my lower back for a total of 4. they are tender and occassionally itch... My sister just went to the doctor 2 days ago with an infection on her upper thigh near her groin. She thought it was an infected Cyst, the doctor says its an absess and cellulitus... What could these bumps be and are they related? Could they just be bug bites or something?