Cluster of bumps located on the inner knee and on the knee of a 1 year old boy?

Picture needed: Has he been crawling on the floor, specifically one with a carpet? If so, rash could be due to allergy to carpet. Without a picture, it's hard to tell what's going on.

Could be a few thing: Could be several things, but commonly is contact irritation, ezcema, etc... Moisture is key on an ongoing basis, as dry skin is irritated skin. It could also be a sign of infection and should be seen by a doctor to be sure. Things like impetigo can cause bumps, most often with crusting and oozing, but can start with simple bumps. Hydrocortisone twice a day with help, but see your doc.