When you have a cold, you may have fever, general discomfort, sneezing and runny nose, but if you have a clear nose at first, but later you find that your nose is yellow and thicker, there are two possibilities: one is the natural process of disease regression, which often results in less runny nose and improvement of other symptoms, and after one or two days, the runny nose becomes even less. There is no need for further medication. The other is a bacterial infection on top of a viral cold, which may cause fever and general discomfort again, and more and more nasal discharge.