The first few years of a child's life are very important to the development of their immune system. As your baby becomes a toddler, they (and you!) will be out and about much more, going to nursery or toddler groups, making new friends and playing outside – all of which means exposure to new kinds of germs. This is perfectly natural and will help their immune system develop.
Let your child eat at their own pace and don't try and insist that the plate is cleared. Rushing your toddler through a meal puts pressure on them, which can reduce their appetite and come across as fussines...