My three year old has nasal congestion, tired, and wants to be held all the time. What can I do to help her symptoms?

Saline spray. Saline nasal stay may help clear his secretions and make him more comfortable. He probably just has a cold. If it lasts over a week or he gets fevers call his pediatrician.
Supportive care. Supportive care is all that is really available for a 3 year old. There are no cold medications approved for this age group. You can try nasal saline and suction to help with the congestion. Make sure he/she is drinking plenty to stay hydrated. If it may be seasonal allergy related, then Benadryl (diphenhydramine) may be an option.