Two year old has pimple like bumps on chin and looks like a light rash on chest and back. no fever, no symptoms. what could it be?

Rash: Difficult to know without seeing it. 1 possibility is that it may be staph or strep on his chin, called impetigo with a more generalized rash that often accompanies it. If this is the case he requires antibiotics to protect particularly his kidneys. Have the rash examined and get a confirmed diagnosis to help with his care. All the best in getting this sorted out.