If you feel the need to help, lean the victim forward so that their head is a little lower than their chest. Support their upper body weight with one arm and use your other hand to strike their back between the shoulder blades. Back blows are never recommended normally however, if the victim is leaning forward the object will move down and out their mouth. Imagine a small baby, less than 12 months. When helping an infant with an airway blockage whether partial or complete, it is dealt with in the same manner.
Abdominal pressure is a last resort with infants because of their liver development.
It's very large at the stage and can be lacerated. The liver holds a large amount of blood and they could bleed to death. Only back blows are performed on infants and it's done by also having the child's head beneath their chest. This way you are working with gravity and not against it. Take care to support a small infant's head and neck by cupping their cheeks with one hand.