There are many different types of cereal out there for infants. There is rice, oatmeal, etc. It depends on the doctor, but looking at infant feeding at a glance solid foods aren't nutritionally needed under 6 months of age.
Then at six months the starter foods are bananas, pears, RICE CEREAL, and applesauce. Strained, purred, fingertipful or small spoonful.
7-9 months are avocados, peaches, carrots, BARLEY CEREAL, teething biscuits, mashed potatoes, squash, prunes, pear and apple juice diluted, sweet potatoes or yams. Pureed and mashed foods. May drink from cup.
9-12 lamb, veal, poultry, tofu, beans, peas, rice cakes, oatmeal, spinach, egg yolk, cheese, yogurt. Lumpier consistency. Finger foods mastered. Bite sized cooked veggies. Melt in mouth foods.
12-18 months whole milk, apricots, cottage chz, grapefruit, ice cream, grape halves, whole eggs, strawberries, beef, tomatoes, fish (salmon), pasta, broccoli, graham crackers, cauliflower, WHEAT CEREAL, melon, honey, mango, pancakes, kiwi, muffins, papaya, bagel. Participates in family meals. Eats chopped and mashed family meals.
With me I was breastfeeding so I did not give my child any cereal, because it was not nutritionally needed. Then when my child started showing signs that she needed more to eat (following my food while I was eating, smacking her lips while watching us eat, etc.) I introduced these foods in order. I prepared them at home organically and pureed them with a blender. Hope this is helpful.
I would also like to add that my daughter's pediatrician informed me that with breast milk other nutrition is not absolutely needed until they are 15 months old. So I would say that your baby is fine without eating the cereal at all if you are nursing.