My 16 mo old has a small isolated cluster of bumps on his stomach. they are tiny and don't seem to itch or be painful but have been there over a week?

More sensitive skin: Toddlers have more sensitive skin. It is thinner and more prone to a little irritation. It is likely something came in contact with his skin that caused some local irritation. Try some over-the-counter strength Hydrocortisone cream, use moisturizers, and keep an eye on it. If it spreads or becomes symptomatic, se doctor for further diagnosis.