My mom has many nodules on her lungs, nausea, fatigue, shortness of breath, and a cough she's had for over a month. could it be serious?

Yes; smoker? Nodules: ... are worrisome in the lungs unless the cause is known to be benign (only way to establish that is by bronchoscopy & biopsy). We don't have all the information here... did your mom ever smoke tobacco? A persistent cough is never a good sign in an (ex-)smoker. Have her talk to a doctor or use HealthTap Prime to go over her history & get a diagnosis. Only then will we know if it's serious or not.