It is not uncommon for a 2-year-old to have a cough, especially upon waking up or going to bed. It is important to pay attention to the type of cough, such as a wet or dry cough, as this can indicate different underlying issues. It is good that the COVID test was negative, ruling out one potential cause. In general, a wet cough is usually not serious but can be bothersome at times. There are non-pharmacological methods to help relieve a cough, such as offering your child plenty of fluids like water or soup, avoiding acidic liquids, and trying honey as a natural remedy. It is generally not recommended to give cough or cold medications to children under 6 years old. Additionally, saline solutions can be used to help clear nasal secretions and improve breathing. If you have further questions or concerns, it is always best to consult with a healthcare professional.